Index: include/clang/AST/Expr.h
===================================================================
--- include/clang/AST/Expr.h
+++ include/clang/AST/Expr.h
@@ -276,6 +276,7 @@
     MLV_LValueCast,           // Specialized form of MLV_InvalidExpression.
     MLV_IncompleteType,
     MLV_ConstQualified,
+    MLV_ConstAddrSpace,
     MLV_ArrayType,
     MLV_NoSetterProperty,
     MLV_MemberFunction,
@@ -324,6 +325,7 @@
       CM_LValueCast, // Same as CM_RValue, but indicates GCC cast-as-lvalue ext
       CM_NoSetterProperty,// Implicit assignment to ObjC property without setter
       CM_ConstQualified,
+      CM_ConstAddrSpace,
       CM_ArrayType,
       CM_IncompleteType
     };
Index: lib/AST/ExprClassification.cpp
===================================================================
--- lib/AST/ExprClassification.cpp
+++ lib/AST/ExprClassification.cpp
@@ -606,7 +606,7 @@
   if (CT.isConstQualified())
     return Cl::CM_ConstQualified;
   if (CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant)
-    return Cl::CM_ConstQualified;
+    return Cl::CM_ConstAddrSpace;
 
   // Arrays are not modifiable, only their elements are.
   if (CT->isArrayType())
@@ -672,6 +672,7 @@
     llvm_unreachable("CM_LValueCast and CL_LValue don't match");
   case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;
   case Cl::CM_ConstQualified: return MLV_ConstQualified;
+  case Cl::CM_ConstAddrSpace: return MLV_ConstAddrSpace;
   case Cl::CM_ArrayType: return MLV_ArrayType;
   case Cl::CM_IncompleteType: return MLV_IncompleteType;
   }
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -9182,6 +9182,9 @@
     }
 
     break;
+  case Expr::MLV_ConstAddrSpace:
+    DiagnoseConstAssignment(S, E, Loc);
+    return true;
   case Expr::MLV_ArrayType:
   case Expr::MLV_ArrayTemporary:
     DiagID = diag::err_typecheck_array_not_modifiable_lvalue;
Index: test/Sema/invalid-assignment-constant-address-space.c
===================================================================
--- /dev/null
+++ test/Sema/invalid-assignment-constant-address-space.c
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only
+
+#define OPENCL_CONSTANT 16776962
+int __attribute__((address_space(OPENCL_CONSTANT))) c[3] = {0};
+
+void foo() {
+  c[0] = 1; //expected-error{{read-only variable is not assignable}}
+}