diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index a527c84..648fe0b 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1744,7 +1744,8 @@
   "__attribute ((NSObject)) may be put on a typedef only, "
   "attribute is ignored">, InGroup<NSobjectAttribute>;
 def warn_attribute_weak_on_local : Warning<
-  "__weak attribute cannot be specified on an automatic variable">,
+  "__weak attribute cannot be specified on an automatic variable when ARC "
+  "is not enabled">,
   InGroup<IgnoredAttributes>;
 def warn_weak_identifier_undeclared : Warning<
   "weak identifier %0 never declared">;
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 4382432..ddb41ed 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -4578,8 +4578,10 @@
       && !NewVD->hasAttr<BlocksAttr>()) {
     if (getLangOpts().getGC() != LangOptions::NonGC)
       Diag(NewVD->getLocation(), diag::warn_gc_attribute_weak_on_local);
-    else
+    else {
+      assert(!getLangOpts().ObjCAutoRefCount);
       Diag(NewVD->getLocation(), diag::warn_attribute_weak_on_local);
+    }
   }
   
   bool isVM = T->isVariablyModifiedType();
diff --git a/test/SemaObjC/nonarc-weak.m b/test/SemaObjC/nonarc-weak.m
new file mode 100644
index 0000000..912a0b1
--- /dev/null
+++ b/test/SemaObjC/nonarc-weak.m
@@ -0,0 +1,16 @@
+// RUN: %clang -fsyntax-only -Wunused-function %s > %t.nonarc 2>&1
+// RUN: %clang -fsyntax-only -Wunused-function -fobjc-arc %s > %t.arc 2>&1
+// RUN: FileCheck -input-file=%t.nonarc %s
+// RUN: FileCheck -input-file=%t.arc -check-prefix=ARC %s
+
+static void bar() {} // Intentionally unused.
+
+void foo(id self) {
+  __weak id weakSelf = self;
+}
+
+// CHECK: 9:13: warning: __weak attribute cannot be specified on an automatic variable when ARC is not enabled
+// CHECK: 6:13: warning: unused function 'bar'
+// CHECK: 2 warnings generated
+// ARC: 6:13: warning: unused function 'bar'
+// ARC: 1 warning generated