diff --git a/Tests/mtiLib/data/mti/gsubalternate.ttx.GSUB b/Tests/mtiLib/data/mti/gsubalternate.ttx.GSUB
index 41843252b..86b0b731b 100644
--- a/Tests/mtiLib/data/mti/gsubalternate.ttx.GSUB
+++ b/Tests/mtiLib/data/mti/gsubalternate.ttx.GSUB
@@ -7,7 +7,7 @@
       <LookupType value="3"/>
       <LookupFlag value="0"/>
       <!-- SubTableCount=1 -->
-      <AlternateSubst index="0" Format="1">
+      <AlternateSubst index="0">
         <AlternateSet glyph="eight">
           <Alternate glyph="uniF738"/>
           <Alternate glyph="uniE0C0"/>
diff --git a/Tests/ttLib/tables/data/aots/gsub3_1_lookupflag_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub3_1_lookupflag_f1.ttx.GSUB
index 43a5e85b3..531c608bd 100644
--- a/Tests/ttLib/tables/data/aots/gsub3_1_lookupflag_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub3_1_lookupflag_f1.ttx.GSUB
@@ -33,7 +33,7 @@
         <LookupType value="3"/>
         <LookupFlag value="2"/><!-- ignoreBaseGlyphs -->
         <!-- SubTableCount=1 -->
-        <AlternateSubst index="0" Format="1">
+        <AlternateSubst index="0">
           <AlternateSet glyph="g18">
             <Alternate glyph="g20"/>
             <Alternate glyph="g21"/>
diff --git a/Tests/ttLib/tables/data/aots/gsub3_1_multiple_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub3_1_multiple_f1.ttx.GSUB
index 1eae117d8..54a52192a 100644
--- a/Tests/ttLib/tables/data/aots/gsub3_1_multiple_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub3_1_multiple_f1.ttx.GSUB
@@ -33,7 +33,7 @@
         <LookupType value="3"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <AlternateSubst index="0" Format="1">
+        <AlternateSubst index="0">
           <AlternateSet glyph="g18">
             <Alternate glyph="g20"/>
             <Alternate glyph="g21"/>
diff --git a/Tests/ttLib/tables/data/aots/gsub3_1_simple_f1.ttx.GSUB b/Tests/ttLib/tables/data/aots/gsub3_1_simple_f1.ttx.GSUB
index 7372cd05c..9a516b27f 100644
--- a/Tests/ttLib/tables/data/aots/gsub3_1_simple_f1.ttx.GSUB
+++ b/Tests/ttLib/tables/data/aots/gsub3_1_simple_f1.ttx.GSUB
@@ -33,7 +33,7 @@
         <LookupType value="3"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <AlternateSubst index="0" Format="1">
+        <AlternateSubst index="0">
           <AlternateSet glyph="g18">
             <Alternate glyph="g20"/>
             <Alternate glyph="g21"/>
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 c83f2346e..3e4997e47 100644
--- a/Tests/varLib/data/master_ttx_interpolatable_otf/TestFamily2-Master0.ttx
+++ b/Tests/varLib/data/master_ttx_interpolatable_otf/TestFamily2-Master0.ttx
@@ -790,7 +790,7 @@
         <LookupType value="3"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <AlternateSubst index="0" Format="1">
+        <AlternateSubst index="0">
           <AlternateSet glyph="a">
             <Alternate glyph="a.alt"/>
             <Alternate glyph="A.sc"/>
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 20c9cb052..9a60e5968 100644
--- a/Tests/varLib/data/master_ttx_interpolatable_ttf/TestFamily2-Master0.ttx
+++ b/Tests/varLib/data/master_ttx_interpolatable_ttf/TestFamily2-Master0.ttx
@@ -1105,7 +1105,7 @@
         <LookupType value="3"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <AlternateSubst index="0" Format="1">
+        <AlternateSubst index="0">
           <AlternateSet glyph="a">
             <Alternate glyph="a.alt"/>
             <Alternate glyph="A.sc"/>
diff --git a/Tests/varLib/data/test_results/InterpolateLayout.ttx b/Tests/varLib/data/test_results/InterpolateLayout.ttx
index 512b97037..64cbd8642 100644
--- a/Tests/varLib/data/test_results/InterpolateLayout.ttx
+++ b/Tests/varLib/data/test_results/InterpolateLayout.ttx
@@ -117,7 +117,7 @@
         <LookupType value="3"/>
         <LookupFlag value="0"/>
         <!-- SubTableCount=1 -->
-        <AlternateSubst index="0" Format="1">
+        <AlternateSubst index="0">
           <AlternateSet glyph="a">
             <Alternate glyph="a.alt"/>
             <Alternate glyph="A.sc"/>