diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 48a747d764a..601d9b42f31 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -29,10 +29,6 @@ static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
     return ConstantInt::get(Val->getType(), 0);
   }
   
-  // Insist that the amount-to-allocate not overflow.
-  OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val);
-  if (OBI && !OBI->hasNoUnsignedWrap()) return 0;
-
   if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
     if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
       if (I->getOpcode() == Instruction::Shl) {
@@ -75,6 +71,11 @@ Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
   // This requires TargetData to get the alloca alignment and size information.
   if (!TD) return 0;
 
+  // Insist that the amount-to-allocate not overflow.
+  OverflowingBinaryOperator *OBI =
+    dyn_cast<OverflowingBinaryOperator>(AI.getOperand(0));
+  if (OBI && !(OBI->hasNoSignedWrap() || OBI->hasNoUnsignedWrap())) return 0;
+
   const PointerType *PTy = cast<PointerType>(CI.getType());
   
   BuilderTy AllocaBuilder(*Builder);