diff --git a/spec/Appendix B -- Grammar Summary.md b/spec/Appendix B -- Grammar Summary.md
index 017efe315..56b7d1676 100644
--- a/spec/Appendix B -- Grammar Summary.md	
+++ b/spec/Appendix B -- Grammar Summary.md	
@@ -210,7 +210,7 @@ TypeExtension :
   - InterfaceTypeExtension
   - UnionTypeExtension
   - EnumTypeExtension
-  - InputObjectTypeDefinition
+  - InputObjectTypeExtension
 
 ScalarTypeDefinition : Description? scalar Name Directives[Const]?