diff --git a/Lib/fontTools/feaLib/ast.py b/Lib/fontTools/feaLib/ast.py
index 3f3bbf883..5289b1002 100644
--- a/Lib/fontTools/feaLib/ast.py
+++ b/Lib/fontTools/feaLib/ast.py
@@ -905,7 +905,9 @@ class MarkMarkPosStatement(Statement):
 
 
 class MultipleSubstStatement(Statement):
-    def __init__(self, prefix, glyph, suffix, replacement, forceChain, location=None):
+    def __init__(
+        self, prefix, glyph, suffix, replacement, forceChain=False, location=None
+    ):
         Statement.__init__(self, location)
         self.prefix, self.glyph, self.suffix = prefix, glyph, suffix
         self.replacement = replacement
diff --git a/Lib/fontTools/feaLib/builder.py b/Lib/fontTools/feaLib/builder.py
index 280eba7fb..456ae3cc7 100644
--- a/Lib/fontTools/feaLib/builder.py
+++ b/Lib/fontTools/feaLib/builder.py
@@ -881,7 +881,7 @@ class Builder(object):
             lookup.ligatures[g] = replacement
 
     def add_multiple_subst(self, location,
-                           prefix, glyph, suffix, replacements, forceChain):
+                           prefix, glyph, suffix, replacements, forceChain=False):
         if prefix or suffix or forceChain:
             chain = self.get_lookup_(location, ChainContextSubstBuilder)
             sub = self.get_chained_lookup_(location, MultipleSubstBuilder)