diff --git a/src/fuse_open.cpp b/src/fuse_open.cpp
index a7b891c5..892ccf87 100644
--- a/src/fuse_open.cpp
+++ b/src/fuse_open.cpp
@@ -38,7 +38,7 @@
 
 struct PT
 {
-  //  std::mutex mutex;
+  std::mutex mutex;
 };
 
 typedef boost::unordered::concurrent_flat_map<std::string,PT> PTMap;;