Index: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1969,7 +1969,7 @@
   "use __attribute__((visibility(\"hidden\"))) attribute instead">;
 
 // C++ Concepts TS
-def err_concept_decl_non_template : Error<
+def err_concept_wrong_decl_kind : Error<
   "'concept' can only appear on the definition of a function template or variable template">;
 def err_concept_decls_may_only_appear_in_namespace_scope : Error<
   "concept declarations may only appear in namespace scope">;
Index: cfe/trunk/lib/Sema/SemaDecl.cpp
===================================================================
--- cfe/trunk/lib/Sema/SemaDecl.cpp
+++ cfe/trunk/lib/Sema/SemaDecl.cpp
@@ -3662,6 +3662,14 @@
     return TagD;
   }
 
+  if (DS.isConceptSpecified()) {
+    // C++ Concepts TS [dcl.spec.concept]p1: A concept definition refers to
+    // either a function concept and its definition or a variable concept and
+    // its initializer.
+    Diag(DS.getConceptSpecLoc(), diag::err_concept_wrong_decl_kind);
+    return TagD;
+  }
+
   DiagnoseFunctionSpecifiers(DS);
 
   if (DS.isFriendSpecified()) {
@@ -4865,7 +4873,7 @@
     // template, declared in namespace scope
     if (!TemplateParamLists.size()) {
       Diag(D.getDeclSpec().getConceptSpecLoc(),
-           diag::err_concept_decl_non_template);
+           diag:: err_concept_wrong_decl_kind);
       return nullptr;
     }
 
Index: cfe/trunk/test/SemaCXX/cxx-concept-declaration.cpp
===================================================================
--- cfe/trunk/test/SemaCXX/cxx-concept-declaration.cpp
+++ cfe/trunk/test/SemaCXX/cxx-concept-declaration.cpp
@@ -23,3 +23,13 @@
 template<typename T>
 concept bool D6; // expected-error {{variable concept declaration must be initialized}}
 
+// Tag
+concept class CC1 {}; // expected-error {{'concept' can only appear on the definition of a function template or variable template}}
+concept struct CS1 {}; // expected-error {{'concept' can only appear on the definition of a function template or variable template}}
+concept union CU1 {}; // expected-error {{'concept' can only appear on the definition of a function template or variable template}}
+concept enum CE1 {}; // expected-error {{'concept' can only appear on the definition of a function template or variable template}}
+template <typename T> concept class TCC1 {}; // expected-error {{'concept' can only appear on the definition of a function template or variable template}}
+template <typename T> concept struct TCS1 {}; // expected-error {{'concept' can only appear on the definition of a function template or variable template}}
+template <typename T> concept union TCU1 {}; // expected-error {{'concept' can only appear on the definition of a function template or variable template}}
+
+concept bool; // expected-error {{'concept' can only appear on the definition of a function template or variable template}}