diff --git a/src/engine/osrm_impl.cpp b/src/engine/osrm_impl.cpp
index 72003eb5ddf..0be92a77776 100644
--- a/src/engine/osrm_impl.cpp
+++ b/src/engine/osrm_impl.cpp
@@ -1,11 +1,3 @@
-namespace boost
-{
-namespace interprocess
-{
-class named_mutex;
-}
-}
-
 #include "engine/osrm_impl.hpp"
 
 #include "engine/plugins/distance_table.hpp"