diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index 8e3ad4c..534a92d 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -969,7 +969,7 @@
     assert(!AdditionalAbiTags &&
            "template template param cannot have abi tags");
     mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
-  } else if (isa<BuiltinTemplateDecl>(ND)) {
+  } else if (isa<BuiltinTemplateDecl>(ND) || isa<ConceptDecl>(ND)) {
     mangleUnscopedName(ND, AdditionalAbiTags);
   } else {
     mangleUnscopedName(ND->getTemplatedDecl(), AdditionalAbiTags);
@@ -1890,7 +1890,7 @@
     mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
   } else {
     manglePrefix(getEffectiveDeclContext(ND), NoFunction);
-    if (isa<BuiltinTemplateDecl>(ND))
+    if (isa<BuiltinTemplateDecl>(ND) || isa<ConceptDecl>(ND))
       mangleUnqualifiedName(ND, nullptr);
     else
       mangleUnqualifiedName(ND->getTemplatedDecl(), nullptr);
@@ -3658,7 +3658,6 @@
   case Expr::ConvertVectorExprClass:
   case Expr::StmtExprClass:
   case Expr::TypeTraitExprClass:
-  case Expr::ConceptSpecializationExprClass:
   case Expr::ArrayTypeTraitExprClass:
   case Expr::ExpressionTraitExprClass:
   case Expr::VAArgExprClass:
@@ -4168,6 +4167,18 @@
     mangleExpression(cast<ParenExpr>(E)->getSubExpr(), Arity);
     break;
 
+
+  case Expr::ConceptSpecializationExprClass: {
+    //  <expr-primary> ::= L <mangled-name> E # external name
+    Out << "L_Z";
+    auto *CSE = cast<ConceptSpecializationExpr>(E);
+    mangleTemplateName(CSE->getNamedConcept(),
+                       CSE->getTemplateArguments().data(),
+                       CSE->getTemplateArguments().size());
+    Out << 'E';
+    break;
+  }
+
   case Expr::DeclRefExprClass:
     mangleDeclRefExpr(cast<DeclRefExpr>(E)->getDecl());
     break;
diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index 2871511..09cc525 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -4302,7 +4302,7 @@
                               TemplateKWLoc, TemplateArgs);
   }
 
-  if (R.getAsSingle<ConceptDecl>() && !AnyDependentArguments()) {
+  if (R.getAsSingle<ConceptDecl>()) {
     return CheckConceptTemplateId(SS, TemplateKWLoc,
                                   R.getLookupNameInfo().getBeginLoc(),
                                   R.getFoundDecl(),
diff --git a/test/CodeGenCXX/mangle-concept.cpp b/test/CodeGenCXX/mangle-concept.cpp
new file mode 100644
index 0000000..8f6d817
--- /dev/null
+++ b/test/CodeGenCXX/mangle-concept.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -verify -Wno-return-type -Wno-main -std=c++2a -fconcepts-ts -emit-llvm -triple %itanium_abi_triple -o - %s | FileCheck %s
+// expected-no-diagnostics
+
+namespace test1 {
+template <bool> struct S {};
+template <typename> concept C = true;
+template <typename T = int> S<C<T>> f0() { return S<C<T>>{}; }
+template S<C<int>> f0<>();
+// CHECK: void @_ZN5test12f0IiEENS_1SIXL_ZNS_1CIT_EEEEEEv()
+}
+
+template <bool> struct S {};
+template <typename> concept C = true;
+template <typename T = int> S<C<T>> f0() { return S<C<T>>{}; }
+template S<C<int>> f0<>();
+// CHECK: void @_Z2f0IiE1SIXL_Z1CIT_EEEEv()
\ No newline at end of file