diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 9eb5993..8fbe82f 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -13979,7 +13979,10 @@
 }
 
 AvailabilityResult Sema::getCurContextAvailability() const {
-  const Decl *D = cast<Decl>(getCurObjCLexicalContext());
+  const Decl *D = cast_or_null<Decl>(getCurObjCLexicalContext());
+  if (!D)
+    return AR_Available;
+
   // If we are within an Objective-C method, we should consult
   // both the availability of the method as well as the
   // enclosing class.  If the class is (say) deprecated,