diff --git a/tools/clang/include/clang/Lex/PreprocessorOptions.h b/tools/clang/include/clang/Lex/PreprocessorOptions.h
index 454b7ac005..fe688e8bec 100644
--- a/tools/clang/include/clang/Lex/PreprocessorOptions.h
+++ b/tools/clang/include/clang/Lex/PreprocessorOptions.h
@@ -149,6 +149,7 @@ class PreprocessorOptions : public RefCountedBase<PreprocessorOptions> {
 public:
   PreprocessorOptions() : UsePredefines(true), DetailedRecord(false),
                           IgnoreLineDirectives(false), // HLSL Change - ignore line directives.
+                          ExpandTokPastingArg(false), // HLSL Change - allow pre-expand
                           DisablePCHValidation(false),
                           AllowPCHWithCompilerErrors(false),
                           DumpDeserializedPCHDecls(false),