diff --git a/lib/Support/StringRef.cpp b/lib/Support/StringRef.cpp
index 14d314b7697..97af0fff5ee 100644
--- a/lib/Support/StringRef.cpp
+++ b/lib/Support/StringRef.cpp
@@ -391,7 +391,7 @@ bool StringRef::getAsInteger(unsigned Radix, APInt &Result) const {
   unsigned BitWidth = Log2Radix * Str.size();
   if (BitWidth < Result.getBitWidth())
     BitWidth = Result.getBitWidth(); // don't shrink the result
-  else
+  else if (BitWidth > Result.getBitWidth())
     Result = Result.zext(BitWidth);
 
   APInt RadixAP, CharAP; // unused unless !IsPowerOf2Radix