diff --git a/clang/include/clang/Lex/LexHLSLRootSignature.h b/clang/include/clang/Lex/LexHLSLRootSignature.h
index 9275e0d75840b..9901485b44d38 100644
--- a/clang/include/clang/Lex/LexHLSLRootSignature.h
+++ b/clang/include/clang/Lex/LexHLSLRootSignature.h
@@ -50,6 +50,10 @@ operator<<(const DiagnosticBuilder &DB, const RootSignatureToken::Kind Kind) {
   case RootSignatureToken::Kind::X:                                            \
     DB << SPELLING;                                                            \
     break;
+#define PUNCTUATOR(X, SPELLING)                                                \
+  case RootSignatureToken::Kind::pu_##X:                                       \
+    DB << #SPELLING;                                                           \
+    break;
 #include "clang/Lex/HLSLRootSignatureTokenKinds.def"
   }
   return DB;
diff --git a/clang/test/SemaHLSL/RootSignature-err.hlsl b/clang/test/SemaHLSL/RootSignature-err.hlsl
index f544247f4db2a..aec8a15f8ed7f 100644
--- a/clang/test/SemaHLSL/RootSignature-err.hlsl
+++ b/clang/test/SemaHLSL/RootSignature-err.hlsl
@@ -18,3 +18,7 @@ void bad_root_signature_3() {}
 
 [RootSignature("DescriptorTable(), invalid")] // expected-error {{expected end of stream to denote end of parameters, or, another valid parameter of RootSignature}}
 void bad_root_signature_4() {}
+
+// expected-error@+1 {{expected ')' to denote end of parameters, or, another valid parameter of RootConstants}}
+[RootSignature("RootConstants(b0, num32BitConstants = 1, invalid)")]
+void bad_root_signature_5() {}