diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index 263af5f0e51..26f6f951333 100644
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -54,7 +54,7 @@ namespace llvm {
   protected:
     virtual ~SCEV();
   public:
-    SCEV(unsigned SCEVTy) : SCEVType(SCEVTy), RefCount(0) {}
+    explicit SCEV(unsigned SCEVTy) : SCEVType(SCEVTy), RefCount(0) {}
 
     /// getNegativeSCEV - Return the SCEV object corresponding to -V.
     ///