diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp
index 47b2b51899c..8c0ab78ba4b 100644
--- a/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -29,7 +29,7 @@
 using namespace llvm;
 
 static cl::opt<bool>
-RunLoopVectorization("vectorize-loops",
+RunLoopVectorization("vectorize-loops", cl::init(false),
                      cl::desc("Run the Loop vectorization passes"));
 
 static cl::opt<bool>