diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 4d0662a7fd0..3718f79a49e 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -5294,8 +5294,8 @@ X86TargetLowering::LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const {
     int MaskVec[] = {
       Reverse1 ? 1 : 0,
       Reverse1 ? 0 : 1,
-      static_cast<int>(Reverse2 ? 1-NumElems :   NumElems),
-      static_cast<int>(Reverse2 ?   NumElems : 1+NumElems)
+      static_cast<int>(Reverse2 ? NumElems+1 : NumElems),
+      static_cast<int>(Reverse2 ? NumElems   : NumElems+1)
     };
     return DAG.getVectorShuffle(VT, dl, V[0], V[1], &MaskVec[0]);
   }