diff --git a/lib/MC/SubtargetFeature.cpp b/lib/MC/SubtargetFeature.cpp
index d72c346..b9caece 100644
--- a/lib/MC/SubtargetFeature.cpp
+++ b/lib/MC/SubtargetFeature.cpp
@@ -128,7 +128,7 @@
   // Binary search the array
   const T *F = std::lower_bound(A, Hi, KV);
   // If not found then return NULL
-  if (F == Hi || std::string(F->Key) != S) return NULL;
+  if (F == Hi || StringRef(F->Key) != S) return NULL;
   // Return the found array item
   return F;
 }