diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 380c737e7e2327b8b63c0cd9ccc4ec6a1409603b..26b411952c71192047be7977aee3908fe25b741c 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -810,7 +810,12 @@ MicrosoftCXXNameMangler::mangleTemplateArgs(
         break;
       }
       /* fallthrough */
-    } default: {
+    }
+    case TemplateArgument::Template:
+    case TemplateArgument::TemplateExpansion:
+    case TemplateArgument::Declaration:
+    case TemplateArgument::NullPtr:
+    case TemplateArgument::Pack: {
       // Issue a diagnostic.
       DiagnosticsEngine &Diags = Context.getDiags();
       unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,