diff --git a/clang/include/clang/Sema/DeclSpec.h b/clang/include/clang/Sema/DeclSpec.h
index f908e91e4bf8..afcd791bca29 100644
--- a/clang/include/clang/Sema/DeclSpec.h
+++ b/clang/include/clang/Sema/DeclSpec.h
@@ -793,6 +793,7 @@ public:
   };
 
   /// PropertyAttributeKind - list of property attributes.
+  /// Keep this list in sync with LLVM's Dwarf.h ApplePropertyAttributes.
   enum ObjCPropertyAttributeKind {
     DQ_PR_noattr = 0x0,
     DQ_PR_readonly = 0x01,