diff --git a/chapi-ast-typescript/src/main/antlr/TypeScriptParser.g4 b/chapi-ast-typescript/src/main/antlr/TypeScriptParser.g4
index ddad5aec..7058cae8 100644
--- a/chapi-ast-typescript/src/main/antlr/TypeScriptParser.g4
+++ b/chapi-ast-typescript/src/main/antlr/TypeScriptParser.g4
@@ -183,7 +183,7 @@ parenthesizedTypeRef
     ;
 
 parameterizedTypeRef
-    : typeName typeArguments?
+    : typeName ('?' | '!')? typeArguments?
     ;
 
 typeName