diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index da59fb5..9eb5993 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2219,8 +2219,18 @@
     const Attr *NewAttribute = NewAttributes[I];
 
     if (isa<AliasAttr>(NewAttribute)) {
-      FunctionDecl *FD = cast<FunctionDecl>(New);
-      S.CheckForFunctionRedefinition(FD, cast<FunctionDecl>(Def));
+      if (FunctionDecl *FD = dyn_cast<FunctionDecl>(New))
+        S.CheckForFunctionRedefinition(FD, cast<FunctionDecl>(Def));
+      else {
+        VarDecl *VD = cast<VarDecl>(New);
+        unsigned Diag = cast<VarDecl>(Def)->isThisDeclarationADefinition() ==
+                                VarDecl::TentativeDefinition
+                            ? diag::err_alias_after_tentative
+                            : diag::err_redefinition;
+        S.Diag(VD->getLocation(), Diag) << VD->getDeclName();
+        S.Diag(Def->getLocation(), diag::note_previous_definition);
+        VD->setInvalidDecl();
+      }
       ++I;
       continue;
     }