diff --git a/lib/VMCore/Constants.cpp b/lib/VMCore/Constants.cpp
index 39c0a8c7010..b9976a72070 100644
--- a/lib/VMCore/Constants.cpp
+++ b/lib/VMCore/Constants.cpp
@@ -1380,7 +1380,7 @@ std::string ConstantArray::getAsString() const {
   std::string Result;
   Result.reserve(getNumOperands());
   for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
-    Result[i] = (char)cast<ConstantInt>(getOperand(i))->getZExtValue();
+    Result.push_back((char)cast<ConstantInt>(getOperand(i))->getZExtValue());
   return Result;
 }