diff --git a/clang/include/clang/Sema/HLSLExternalSemaSource.h b/clang/include/clang/Sema/HLSLExternalSemaSource.h
--- a/clang/include/clang/Sema/HLSLExternalSemaSource.h
+++ b/clang/include/clang/Sema/HLSLExternalSemaSource.h
@@ -45,6 +45,7 @@
   /// Inform the semantic consumer that Sema is no longer available.
   void ForgetSema() override { SemaPtr = nullptr; }
 
+  using ExternalASTSource::CompleteType;
   /// Complete an incomplete HLSL builtin type
   void CompleteType(TagDecl *Tag) override;
 };