Index: SemaInit.cpp
===================================================================
--- SemaInit.cpp
+++ SemaInit.cpp
@@ -2261,14 +2261,16 @@
                  && "A union should never have more than one initializer!");
 
           // We're about to throw away an initializer, emit warning.
-          SemaRef.Diag(D->getFieldLoc(),
-                       diag::warn_initializer_overrides)
-            << D->getSourceRange();
           Expr *ExistingInit = StructuredList->getInit(0);
-          SemaRef.Diag(ExistingInit->getLocStart(),
-                       diag::note_previous_initializer)
-            << /*FIXME:has side effects=*/0
-            << ExistingInit->getSourceRange();
+          if (ExistingInit) {
+            SemaRef.Diag(D->getFieldLoc(),
+                         diag::warn_initializer_overrides)
+              << D->getSourceRange();
+            SemaRef.Diag(ExistingInit->getLocStart(),
+                         diag::note_previous_initializer)
+              << /*FIXME:has side effects=*/0
+              << ExistingInit->getSourceRange();
+          }
 
           // remove existing initializer
           StructuredList->resizeInits(SemaRef.Context, 0);