diff --git a/Tests/mtiLib/data/mti/gsubmultiple.ttx.GSUB b/Tests/mtiLib/data/mti/gsubmultiple.ttx.GSUB
index a68a45a90..5bedfba6a 100644
--- a/Tests/mtiLib/data/mti/gsubmultiple.ttx.GSUB
+++ b/Tests/mtiLib/data/mti/gsubmultiple.ttx.GSUB
@@ -7,7 +7,7 @@
       <LookupType value="2"/>
       <LookupFlag value="0"/>
       <!-- SubTableCount=1 -->
-      <MultipleSubst index="0" Format="1">
+      <MultipleSubst index="0">
         <Substitution in="janyevoweltelugu" out="jaivoweltelugu,nyasubscripttelugu"/>
         <Substitution in="kassevoweltelugu" out="kaivoweltelugu,ssasubscripttelugu"/>
       </MultipleSubst>
diff --git a/Tests/otlLib/data/gsub_51.ttx b/Tests/otlLib/data/gsub_51.ttx
index 86f0f66bd..0e6a41338 100644
--- a/Tests/otlLib/data/gsub_51.ttx
+++ b/Tests/otlLib/data/gsub_51.ttx
@@ -117,7 +117,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/otlLib/data/gsub_52.ttx b/Tests/otlLib/data/gsub_52.ttx
index 6b26e7877..4e83b96db 100644
--- a/Tests/otlLib/data/gsub_52.ttx
+++ b/Tests/otlLib/data/gsub_52.ttx
@@ -117,7 +117,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub2_1_lookupflag_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub2_1_lookupflag_f1.ttx.GSUB
index d3f65be15..d3c37dca1 100644
--- a/Tests/ttLib/tables/data/aots/gsub2_1_lookupflag_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub2_1_lookupflag_f1.ttx.GSUB
@@ -33,7 +33,7 @@
         <LookupType value="2"/>
         <LookupFlag value="2"/><!-- ignoreBaseGlyphs -->
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g18" out="g20,g21"/>
           <Substitution in="g19" out="g22,g23"/>
         </MultipleSubst>
diff --git a/Tests/ttLib/tables/data/aots/gsub2_1_multiple_sequences_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub2_1_multiple_sequences_f1.ttx.GSUB
index 5ec800e57..1c4cd4ca5 100644
--- a/Tests/ttLib/tables/data/aots/gsub2_1_multiple_sequences_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub2_1_multiple_sequences_f1.ttx.GSUB
@@ -33,7 +33,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g18" out="g20,g21"/>
           <Substitution in="g19" out="g22,g23"/>
         </MultipleSubst>
diff --git a/Tests/ttLib/tables/data/aots/gsub2_1_simple_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub2_1_simple_f1.ttx.GSUB
index cae4f6630..b2453ecda 100644
--- a/Tests/ttLib/tables/data/aots/gsub2_1_simple_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub2_1_simple_f1.ttx.GSUB
@@ -33,7 +33,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g18" out="g20,g21,g22"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f1.ttx.GSUB
index ee74866be..897946e95 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f2.ttx.GSUB
index 3b6e0cb83..896736c2a 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f3.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f3.ttx.GSUB
index 92069ec5b..43a591479 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f3.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f3.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f4.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f4.ttx.GSUB
index 69409f471..d649b637f 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f4.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_boundary_f4.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_lookupflag_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_lookupflag_f1.ttx.GSUB
index e9cf696c9..dd83bd7ec 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_lookupflag_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_lookupflag_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_multiple_subrules_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_multiple_subrules_f1.ttx.GSUB
index f6a979307..b446f6264 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_multiple_subrules_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_multiple_subrules_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_multiple_subrules_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_multiple_subrules_f2.ttx.GSUB
index 1865fc8b8..9b6b835b4 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_multiple_subrules_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_multiple_subrules_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_next_glyph_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_next_glyph_f1.ttx.GSUB
index 73eb6396c..8b554abd3 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_next_glyph_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_next_glyph_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_simple_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_simple_f1.ttx.GSUB
index 1fa4e823c..f7dbe588e 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_simple_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_simple_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_simple_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_simple_f2.ttx.GSUB
index c482c26c0..a8894e53b 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_simple_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_simple_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining1_successive_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining1_successive_f1.ttx.GSUB
index 5dba25448..52cf963a4 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining1_successive_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining1_successive_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f1.ttx.GSUB
index 020fb1efe..9109e5969 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f2.ttx.GSUB
index 9217e0910..ead59dc9b 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f3.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f3.ttx.GSUB
index fa3b04bd7..8163db119 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f3.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f3.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f4.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f4.ttx.GSUB
index 7ebeb58c5..48f948361 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f4.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_boundary_f4.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_lookupflag_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_lookupflag_f1.ttx.GSUB
index aefb46cb9..a7f4ce6cf 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_lookupflag_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_lookupflag_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_multiple_subrules_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_multiple_subrules_f1.ttx.GSUB
index 969c91d2f..34cea465c 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_multiple_subrules_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_multiple_subrules_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_multiple_subrules_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_multiple_subrules_f2.ttx.GSUB
index f265ed148..21cbe2a9d 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_multiple_subrules_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_multiple_subrules_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_next_glyph_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_next_glyph_f1.ttx.GSUB
index 322f89154..d14ac1b9a 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_next_glyph_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_next_glyph_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_simple_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_simple_f1.ttx.GSUB
index bec940175..da6a915c0 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_simple_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_simple_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_simple_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_simple_f2.ttx.GSUB
index 21e389424..94f62173d 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_simple_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_simple_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining2_successive_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining2_successive_f1.ttx.GSUB
index b4c1d4f74..7dbc5e039 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining2_successive_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining2_successive_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f1.ttx.GSUB
index 8aac90344..82eb13312 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f2.ttx.GSUB
index 5ddafa255..b5c16361f 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f3.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f3.ttx.GSUB
index 5c0265c04..76d5a4625 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f3.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f3.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f4.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f4.ttx.GSUB
index e52ca51f2..9346d47bf 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f4.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining3_boundary_f4.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining3_lookupflag_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining3_lookupflag_f1.ttx.GSUB
index b83190980..c329936e0 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining3_lookupflag_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining3_lookupflag_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining3_next_glyph_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining3_next_glyph_f1.ttx.GSUB
index 8801bed33..46d1f8594 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining3_next_glyph_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining3_next_glyph_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining3_simple_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining3_simple_f1.ttx.GSUB
index 9b8f7e156..722dcadb6 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining3_simple_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining3_simple_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining3_simple_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining3_simple_f2.ttx.GSUB
index f568a3807..5842c5549 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining3_simple_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining3_simple_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_chaining3_successive_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_chaining3_successive_f1.ttx.GSUB
index 68d5abae7..610ea565b 100644
--- a/Tests/ttLib/tables/data/aots/gsub_chaining3_successive_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_chaining3_successive_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_boundary_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_boundary_f1.ttx.GSUB
index 94df4e8af..6de650669 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_boundary_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_boundary_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_boundary_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_boundary_f2.ttx.GSUB
index 58191c167..7d5772c35 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_boundary_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_boundary_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_expansion_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_expansion_f1.ttx.GSUB
index 95d7c6d49..e8dca8a8e 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_expansion_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_expansion_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_lookupflag_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_lookupflag_f1.ttx.GSUB
index 3ade9e951..579294fba 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_lookupflag_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_lookupflag_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_lookupflag_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_lookupflag_f2.ttx.GSUB
index efb4aeb8e..e583f6a1f 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_lookupflag_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_lookupflag_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_multiple_subrules_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_multiple_subrules_f1.ttx.GSUB
index f441d4d99..220232081 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_multiple_subrules_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_multiple_subrules_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_multiple_subrules_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_multiple_subrules_f2.ttx.GSUB
index 9cb0fbf71..df568c31c 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_multiple_subrules_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_multiple_subrules_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_next_glyph_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_next_glyph_f1.ttx.GSUB
index 238cc6c18..518e7549b 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_next_glyph_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_next_glyph_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_simple_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_simple_f1.ttx.GSUB
index cb4bc4fdb..2906b061e 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_simple_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_simple_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_simple_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_simple_f2.ttx.GSUB
index b31eae8ff..554168b94 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_simple_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_simple_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context1_successive_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context1_successive_f1.ttx.GSUB
index 63dcdc545..fc66abd50 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context1_successive_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context1_successive_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_boundary_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_boundary_f1.ttx.GSUB
index 76bf0cb4b..e1e12f8d2 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_boundary_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_boundary_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_boundary_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_boundary_f2.ttx.GSUB
index a963b3da8..d2598d954 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_boundary_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_boundary_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_classes_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_classes_f1.ttx.GSUB
index 463f1c053..394df78af 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_classes_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_classes_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_classes_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_classes_f2.ttx.GSUB
index 20b643dbe..4de5bc626 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_classes_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_classes_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_expansion_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_expansion_f1.ttx.GSUB
index d64741952..5ab7d08ef 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_expansion_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_expansion_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_lookupflag_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_lookupflag_f1.ttx.GSUB
index 19da246a6..4a8d74935 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_lookupflag_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_lookupflag_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_lookupflag_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_lookupflag_f2.ttx.GSUB
index 0d5a49c9d..a672edf1e 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_lookupflag_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_lookupflag_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_multiple_subrules_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_multiple_subrules_f1.ttx.GSUB
index 4bd99cb18..07b5f5ebf 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_multiple_subrules_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_multiple_subrules_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_multiple_subrules_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_multiple_subrules_f2.ttx.GSUB
index 43052de0c..22527617f 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_multiple_subrules_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_multiple_subrules_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_next_glyph_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_next_glyph_f1.ttx.GSUB
index fdbea86af..b78220bdb 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_next_glyph_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_next_glyph_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_simple_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_simple_f1.ttx.GSUB
index 3c3b0b43f..35fff94c0 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_simple_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_simple_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_simple_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_simple_f2.ttx.GSUB
index 03c2d7790..28ab11ee3 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_simple_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_simple_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context2_successive_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context2_successive_f1.ttx.GSUB
index 3346c15ce..a3642077c 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context2_successive_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context2_successive_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context3_boundary_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context3_boundary_f1.ttx.GSUB
index 066e63530..9a73fac0e 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context3_boundary_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context3_boundary_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context3_boundary_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context3_boundary_f2.ttx.GSUB
index bea7f48a7..d45e67b9b 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context3_boundary_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context3_boundary_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context3_lookupflag_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context3_lookupflag_f1.ttx.GSUB
index 7917f83a0..90b53f45e 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context3_lookupflag_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context3_lookupflag_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context3_lookupflag_f2.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context3_lookupflag_f2.ttx.GSUB
index ed9352e7a..a82c3c0d8 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context3_lookupflag_f2.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context3_lookupflag_f2.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context3_next_glyph_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context3_next_glyph_f1.ttx.GSUB
index 33e50d06a..a4f5addc8 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context3_next_glyph_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context3_next_glyph_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context3_simple_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context3_simple_f1.ttx.GSUB
index 53f97c70b..15d6c087b 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context3_simple_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context3_simple_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/ttLib/tables/data/aots/gsub_context3_successive_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub_context3_successive_f1.ttx.GSUB
index f73628502..6558c692f 100644
--- a/Tests/ttLib/tables/data/aots/gsub_context3_successive_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub_context3_successive_f1.ttx.GSUB
@@ -70,7 +70,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="g21" out="g61,g62,g63"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/varLib/data/master_ttx_interpolatable_otf/TestFamily2-Master0.ttx b/Tests/varLib/data/master_ttx_interpolatable_otf/TestFamily2-Master0.ttx
index 3e4997e47..157043f03 100644
--- a/Tests/varLib/data/master_ttx_interpolatable_otf/TestFamily2-Master0.ttx
+++ b/Tests/varLib/data/master_ttx_interpolatable_otf/TestFamily2-Master0.ttx
@@ -782,7 +782,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="ampersand" out="a,n,d"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/varLib/data/master_ttx_interpolatable_ttf/TestFamily2-Master0.ttx b/Tests/varLib/data/master_ttx_interpolatable_ttf/TestFamily2-Master0.ttx
index 9a60e5968..d1a339351 100644
--- a/Tests/varLib/data/master_ttx_interpolatable_ttf/TestFamily2-Master0.ttx
+++ b/Tests/varLib/data/master_ttx_interpolatable_ttf/TestFamily2-Master0.ttx
@@ -1097,7 +1097,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="ampersand" out="a,n,d"/>
         </MultipleSubst>
       </Lookup>
diff --git a/Tests/varLib/data/test_results/InterpolateLayout.ttx b/Tests/varLib/data/test_results/InterpolateLayout.ttx
index 64cbd8642..81e50fbf6 100644
--- a/Tests/varLib/data/test_results/InterpolateLayout.ttx
+++ b/Tests/varLib/data/test_results/InterpolateLayout.ttx
@@ -109,7 +109,7 @@
         <LookupType value="2"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <MultipleSubst index="0" Format="1">
+        <MultipleSubst index="0">
           <Substitution in="ampersand" out="a,n,d"/>
         </MultipleSubst>
       </Lookup>