diff --git a/lib/Bytecode/Writer/SlotCalculator.cpp b/lib/Bytecode/Writer/SlotCalculator.cpp
index d4145dbcdca..0f298dcd003 100644
--- a/lib/Bytecode/Writer/SlotCalculator.cpp
+++ b/lib/Bytecode/Writer/SlotCalculator.cpp
@@ -150,7 +150,8 @@ void SlotCalculator::processModule() {
         TypePlane &Plane = Table[plane];
         unsigned FirstNonStringID = 0;
         for (unsigned i = 0, e = Plane.size(); i != e; ++i)
-          if (isa<ConstantAggregateZero>(Plane[i]) ||
+          if (isa<ConstantAggregateZero>(Plane[i]) || 
+	      isa<UndefValue>(Plane[i]) ||
               cast<ConstantArray>(Plane[i])->isString()) {
             // Check to see if we have to shuffle this string around.  If not,
             // don't do anything.