diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -16598,6 +16598,19 @@
 
   // Make the previous decl visible.
   makeMergedDefinitionVisible(SkipBody.Previous);
+  // For the ignored `EnumDecl` definition remove its `EnumConstantDecl` from
+  // global name lookup to avoid future ambiguous lookups. Doing this for ObjC/C
+  // to mimic early return in `Sema::ActOnTag` that avoids calling
+  // `PushOnScopeChains` for duplicate `TagDecl` definitions. Doing it only for
+  // `EnumDecl` among all `TagDecl` because enum constants have global name
+  // lookup while record field lookup is limited to a record.
+  if (!getLangOpts().CPlusPlus) {
+    if (const auto *ED = dyn_cast<EnumDecl>(SkipBody.New))
+      for (EnumDecl::enumerator_iterator EC = ED->enumerator_begin(),
+                                         End = ED->enumerator_end();
+           EC != End; ++EC)
+        IdResolver.RemoveDecl(*EC);
+  }
   return true;
 }
 
diff --git a/clang/test/Modules/redefinition-c-tagtypes.m b/clang/test/Modules/redefinition-c-tagtypes.m
--- a/clang/test/Modules/redefinition-c-tagtypes.m
+++ b/clang/test/Modules/redefinition-c-tagtypes.m
@@ -32,6 +32,10 @@
   TRD = 55
 };
 
+int testReferencingNSEConstant() {
+  return FST;
+}
+
 #define NS_ENUM(_type, _name) \
   enum _name : _type _name;   \
   enum _name : _type
@@ -42,7 +46,11 @@
   MinXOther = MinX,
 #else
   MinXOther = TRD, // expected-note {{enumerator 'MinXOther' with value 55 here}}
-  // expected-error@redefinition-c-tagtypes.m:39 {{type 'enum NSMyEnum' has incompatible definitions}}
+  // expected-error@redefinition-c-tagtypes.m:43 {{type 'enum NSMyEnum' has incompatible definitions}}
   // expected-note@Inputs/F.framework/PrivateHeaders/NS.h:18 {{enumerator 'MinXOther' with value 11 here}}
 #endif
 };
+
+int testReferencingNSMyEnumConstant() {
+  return MinX;
+}