diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -2581,6 +2581,8 @@
 
   TypeSourceInfo *TInfo = nullptr;
   GetTypeFromParser(basetype, &TInfo);
+  if (TInfo == nullptr)
+    return true;
 
   if (EllipsisLoc.isInvalid() &&
       DiagnoseUnexpandedParameterPack(SpecifierRange.getBegin(), TInfo,