Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -14896,6 +14896,8 @@
     default:
       return ExprEvaluatorBaseTy::VisitCastExpr(E);
     case CK_NullToPointer:
+      VisitIgnoredValue(E->getSubExpr());
+      return ZeroInitialization(E);
     case CK_NonAtomicToAtomic:
       return This ? EvaluateInPlace(Result, Info, *This, E->getSubExpr())
                   : Evaluate(Result, Info, E->getSubExpr());
Index: clang/test/CodeGen/atomic.c
===================================================================
--- clang/test/CodeGen/atomic.c
+++ clang/test/CodeGen/atomic.c
@@ -1,6 +1,7 @@
 // RUN: %clang_cc1 %s -emit-llvm -o - -triple=i686-apple-darwin9 | FileCheck %s
 
 // CHECK: @[[GLOB_POINTER:.+]] = internal global ptr null
+// CHECK: @[[GLOB_POINTER_FROM_INT:.+]] = internal global ptr null
 // CHECK: @[[GLOB_INT:.+]] = internal global i32 0
 // CHECK: @[[GLOB_FLT:.+]] = internal global float {{[0e\+-\.]+}}, align
 
@@ -125,6 +126,7 @@
 
 // Ensure that global initialization of atomics is correct.
 static _Atomic(int *) glob_pointer = (void *)0;
+static _Atomic(int *) glob_pointer_from_int = 0;
 static _Atomic int glob_int = 0;
 static _Atomic float glob_flt = 0.0f;
 
@@ -132,6 +134,9 @@
   (void)glob_pointer;
   // CHECK: %[[LOCAL_INT:.+]] = load atomic i32, ptr @[[GLOB_POINTER]] seq_cst
   // CHECK-NEXT: inttoptr i32 %[[LOCAL_INT]] to ptr
+  (void)glob_pointer_from_int;
+  // CHECK: %[[LOCAL_INT_2:.+]] = load atomic i32, ptr @[[GLOB_POINTER_FROM_INT]] seq_cst
+  // CHECK-NEXT: inttoptr i32 %[[LOCAL_INT_2]] to ptr
   (void)glob_int;
   // CHECK: load atomic i32, ptr @[[GLOB_INT]] seq_cst
   (void)glob_flt;