Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -8297,6 +8297,8 @@
   "sampler_t variable required - got %0">;
 def err_wrong_sampler_addressspace: Error<
   "sampler type cannot be used with the __local and __global address space qualifiers">;
+def err_opencl_sampler_qualifier : Error<
+  "global sampler requires a const qualifier">;
 def err_opencl_cast_non_zero_to_event_t : Error<
   "cannot cast non-zero value '%0' to 'event_t'">;
 def err_opencl_global_invalid_addr_space : Error<
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -6070,12 +6070,24 @@
       }
     }
 
-    // OpenCL v1.2 s6.9.b p4:
-    // The sampler type cannot be used with the __local and __global address
-    // space qualifiers.
-    if (R->isSamplerT() && (R.getAddressSpace() == LangAS::opencl_local ||
-      R.getAddressSpace() == LangAS::opencl_global)) {
-      Diag(D.getIdentifierLoc(), diag::err_wrong_sampler_addressspace);
+    if (R->isSamplerT()) {
+      // OpenCL v1.2 s6.9.b p4:
+      // The sampler type cannot be used with the __local and __global address
+      // space qualifiers.
+      if (R.getAddressSpace() == LangAS::opencl_local ||
+          R.getAddressSpace() == LangAS::opencl_global) {
+        Diag(D.getIdentifierLoc(), diag::err_wrong_sampler_addressspace);
+      }
+
+      // OpenCL v1.2 s6.12.14.1:
+      // A global sampler must be declared with either the constant address
+      // space qualifier or with the const qualifier.
+      if (DC->isTranslationUnit() &&
+          !(R.getAddressSpace() == LangAS::opencl_constant ||
+          R.isConstQualified())) {
+        Diag(D.getIdentifierLoc(), diag::err_opencl_sampler_qualifier);
+        D.setInvalidType();
+      }
     }
 
     // OpenCL v1.2 s6.9.r:
Index: test/SemaOpenCL/sampler_t.cl
===================================================================
--- test/SemaOpenCL/sampler_t.cl
+++ test/SemaOpenCL/sampler_t.cl
@@ -9,7 +9,7 @@
 
 constant sampler_t glb_smp = CLK_ADDRESS_CLAMP_TO_EDGE | CLK_NORMALIZED_COORDS_TRUE | CLK_FILTER_LINEAR;
 constant sampler_t glb_smp2; // expected-error{{variable in constant address space must be initialized}}
-global sampler_t glb_smp3 = CLK_ADDRESS_CLAMP_TO_EDGE | CLK_NORMALIZED_COORDS_TRUE | CLK_FILTER_NEAREST; // expected-error{{sampler type cannot be used with the __local and __global address space qualifiers}}
+global sampler_t glb_smp3 = CLK_ADDRESS_CLAMP_TO_EDGE | CLK_NORMALIZED_COORDS_TRUE | CLK_FILTER_NEAREST; // expected-error{{sampler type cannot be used with the __local and __global address space qualifiers}} expected-error {{global sampler requires a const qualifier}}
 
 constant sampler_t glb_smp4 = 0;
 #ifdef CHECK_SAMPLER_VALUE
@@ -38,6 +38,8 @@
 
 sampler_t bad(void); //expected-error{{declaring function return value of type 'sampler_t' is not allowed}}
 
+sampler_t global_nonconst_smp = 0; // expected-error {{global sampler requires a const qualifier}}
+
 void kernel ker(sampler_t argsmp) {
   local sampler_t smp; // expected-error{{sampler type cannot be used with the __local and __global address space qualifiers}}
   const sampler_t const_smp = CLK_ADDRESS_CLAMP_TO_EDGE | CLK_NORMALIZED_COORDS_TRUE | CLK_FILTER_LINEAR;