diff --git a/lib/Bytecode/Writer/SlotCalculator.cpp b/lib/Bytecode/Writer/SlotCalculator.cpp
index 0f298dcd003..575dd34dbdf 100644
--- a/lib/Bytecode/Writer/SlotCalculator.cpp
+++ b/lib/Bytecode/Writer/SlotCalculator.cpp
@@ -151,8 +151,8 @@ void SlotCalculator::processModule() {
         unsigned FirstNonStringID = 0;
         for (unsigned i = 0, e = Plane.size(); i != e; ++i)
           if (isa<ConstantAggregateZero>(Plane[i]) || 
-	      isa<UndefValue>(Plane[i]) ||
-              cast<ConstantArray>(Plane[i])->isString()) {
+	      (isa<ConstantArray>(Plane[i]) &&
+               cast<ConstantArray>(Plane[i])->isString())) {
             // Check to see if we have to shuffle this string around.  If not,
             // don't do anything.
             if (i != FirstNonStringID) {