Index: clang/lib/AST/ODRHash.cpp
===================================================================
--- clang/lib/AST/ODRHash.cpp
+++ clang/lib/AST/ODRHash.cpp
@@ -72,7 +72,7 @@
     AddBoolean(S.isUnarySelector());
     unsigned NumArgs = S.getNumArgs();
     for (unsigned i = 0; i < NumArgs; ++i) {
-      AddIdentifierInfo(S.getIdentifierInfoForSlot(i));
+      ID.AddString(S.getNameForSlot(i));
     }
     break;
   }
Index: clang/test/Modules/odr_hash.mm
===================================================================
--- clang/test/Modules/odr_hash.mm
+++ clang/test/Modules/odr_hash.mm
@@ -57,6 +57,10 @@
 @interface Interface3 <T : I1 *>
 @end
 
+@interface EmptySelectorSlot
+- (void)notify:(int)arg :(int)empty;
+@end
+
 #endif
 
 #if defined(FIRST)
@@ -289,6 +293,14 @@
 }  // namespace ObjCTypeParam
 }  // namespace Types
 
+namespace rdar51615164 {
+#if defined(FIRST) || defined(SECOND)
+void notify(EmptySelectorSlot *obj) {
+  [obj notify:0 :0];
+}
+#endif
+}  // namespace rdar51615164
+
 // Keep macros contained to one file.
 #ifdef FIRST
 #undef FIRST