Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -5241,6 +5241,9 @@
 def err_standalone_class_nested_name_specifier : Error<
   "forward declaration of %select{class|struct|interface|union|enum}0 cannot "
   "have a nested name specifier">;
+def err_standalone_class_specifier : Error<
+  "forward declaration of qualified %select{class|struct|interface|union|enum}0 "
+	"not allowed">;
 def err_typecheck_sclass_func : Error<"illegal storage class on function">;
 def err_static_block_func : Error<
   "function declared in block scope cannot have 'static' storage class">;
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -3789,6 +3789,17 @@
   if (Tag && SS.isNotEmpty() && !Tag->isCompleteDefinition() &&
       !IsExplicitInstantiation && !IsExplicitSpecialization &&
       !isa<ClassTemplatePartialSpecializationDecl>(Tag)) {
+    
+    // Per C++ standard [n3485] 3.4.4 Elaborated type specifiers, section 3:
+    // "Cannot introduce an qualified".
+    // A clang::NestedNameSpecifier can represent many kinds of specifiers.
+    // A global-specifier with no nested-name-specifier requires a different
+    // diagnostic from a nested-name specifier.
+    unsigned diagId = ( SS.getScopeRep()->getKind() == NestedNameSpecifier::Global &&
+      !SS.getScopeRep()->getPrefix() )
+      ? diag::err_standalone_class_specifier
+      : diagId = diag::err_standalone_class_nested_name_specifier;
+
     // Per C++ [dcl.type.elab]p1, a class declaration cannot have a
     // nested-name-specifier unless it is an explicit instantiation
     // or an explicit specialization.
@@ -3797,8 +3808,9 @@
     // obvious intent of DR1819.
     //
     // Per C++ [dcl.enum]p1, an opaque-enum-declaration can't either.
-    Diag(SS.getBeginLoc(), diag::err_standalone_class_nested_name_specifier)
-        << GetDiagnosticTypeSpecifierID(DS.getTypeSpecType()) << SS.getRange();
+    Diag(SS.getBeginLoc(), diagId)
+      << GetDiagnosticTypeSpecifierID(DS.getTypeSpecType()) << SS.getRange();
+
     return nullptr;
   }