diff --git a/src/mergerfs.cpp b/src/mergerfs.cpp
index 8f73bad3..8a3b8760 100644
--- a/src/mergerfs.cpp
+++ b/src/mergerfs.cpp
@@ -332,6 +332,8 @@ namespace l
   }
 }
 
+#include <boost/unordered/concurrent_flat_map.hpp>
+
 int
 main(int    argc_,
      char **argv_)