diff --git a/include/llvm/ADT/DenseSet.h b/include/llvm/ADT/DenseSet.h
index 1a1de8b76f9..b19dc5e2fc3 100644
--- a/include/llvm/ADT/DenseSet.h
+++ b/include/llvm/ADT/DenseSet.h
@@ -38,7 +38,7 @@ public:
     TheMap.clear();
   }
   
-  bool count(const ValueT &V) {
+  bool count(const ValueT &V) const {
     return TheMap.count(V);
   }