diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -1020,7 +1020,7 @@
   if (CI.getLangOpts().HLSL && CI.hasASTContext()) {
     IntrusiveRefCntPtr<ExternalASTSource> HLSLSema(
         new HLSLExternalSemaSource());
-    CI.getASTContext().setExternalSource(HLSLSema);
+    CI.setExternalSemaSource(HLSLSema);
   }
 
   FailureCleanup.release();