Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -1967,7 +1967,7 @@
 def NSErrorDomain : InheritableAttr {
   let Spellings = [GNU<"ns_error_domain">];
   let Subjects = SubjectList<[Enum], ErrorDiag>;
-  let Args = [DeclArgument<Var, "ErrorDomain">];
+  let Args = [IdentifierArgument<"ErrorDomain">];
   let Documentation = [NSErrorDomainDocs];
 }
 
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -9683,8 +9683,6 @@
   " attributes">;
 def err_nserrordomain_invalid_decl : Error<
   "domain argument %select{|%1 }0does not refer to global constant">;
-def err_nserrordomain_wrong_type : Error<
-  "domain argument %0 does not point to an NSString or CFString constant">;
 
 def warn_nsconsumed_attribute_mismatch : Warning<
   err_nsconsumed_attribute_mismatch.Text>, InGroup<NSConsumedMismatch>;
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -5510,28 +5510,28 @@
 }
 
 static void handleNSErrorDomain(Sema &S, Decl *D, const ParsedAttr &AL) {
-  auto *E = AL.getArgAsExpr(0);
-  auto Loc = E ? E->getBeginLoc() : AL.getLoc();
+  IdentifierLoc *IdentLoc = AL.isArgIdent(0) ? AL.getArgAsIdent(0) : nullptr;
+  if (!IdentLoc || !IdentLoc->Ident) {
+    // Try to locate the argument directly
+    SourceLocation Loc = AL.getLoc();
+    if (AL.isArgExpr(0) && AL.getArgAsExpr(0))
+      Loc = AL.getArgAsExpr(0)->getBeginLoc();
 
-  auto *DRE = dyn_cast<DeclRefExpr>(AL.getArgAsExpr(0));
-  if (!DRE) {
     S.Diag(Loc, diag::err_nserrordomain_invalid_decl) << 0;
     return;
   }
 
-  auto *VD = dyn_cast<VarDecl>(DRE->getDecl());
-  if (!VD) {
-    S.Diag(Loc, diag::err_nserrordomain_invalid_decl) << 1 << DRE->getDecl();
+  // Verify that the identifier is a valid decl in the C decl namespace
+  LookupResult LR(S, DeclarationName(IdentLoc->Ident), SourceLocation(),
+                  Sema::LookupNameKind::LookupOrdinaryName);
+  if (!S.LookupName(LR, S.TUScope) || !LR.getAsSingle<VarDecl>()) {
+    S.Diag(IdentLoc->Loc, diag::err_nserrordomain_invalid_decl)
+        << 1 << IdentLoc->Ident;
     return;
   }
 
-  if (!isNSStringType(VD->getType(), S.Context) &&
-      !isCFStringType(VD->getType(), S.Context)) {
-    S.Diag(Loc, diag::err_nserrordomain_wrong_type) << VD;
-    return;
-  }
-
-  D->addAttr(::new (S.Context) NSErrorDomainAttr(S.Context, AL, VD));
+  D->addAttr(::new (S.Context)
+                 NSErrorDomainAttr(S.Context, AL, IdentLoc->Ident));
 }
 
 static void handleObjCBridgeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
Index: clang/test/Sema/ns_error_enum.m
===================================================================
--- clang/test/Sema/ns_error_enum.m
+++ clang/test/Sema/ns_error_enum.m
@@ -53,7 +53,6 @@
 
 extern char *const WrongErrorDomainType;
 enum __attribute__((ns_error_domain(WrongErrorDomainType))) MyWrongErrorDomainType { MyWrongErrorDomain };
-// expected-error@-1{{domain argument 'WrongErrorDomainType' does not point to an NSString or CFString constant}}
 
 struct __attribute__((ns_error_domain(MyErrorDomain))) MyStructWithErrorDomain {};
 // expected-error@-1{{'ns_error_domain' attribute only applies to enums}}
@@ -68,7 +67,7 @@
 // expected-error@-1{{'ns_error_domain' attribute takes one argument}}
 
 typedef NS_ERROR_ENUM(unsigned char, MyErrorEnumInvalid, InvalidDomain) {
-	// expected-error@-1{{use of undeclared identifier 'InvalidDomain'}}
+	// expected-error@-1{{domain argument 'InvalidDomain' does not refer to global constant}}
 	MyErrFirstInvalid,
 	MyErrSecondInvalid,
 };