diff --git a/dumux/linear/vertexborderlistfromgrid.hh b/dumux/linear/vertexborderlistfromgrid.hh
index 662907dece994d504912d6b49ed941016f6003b2..d88b07b2924953e013e3475c91a949e4de1add9d 100644
--- a/dumux/linear/vertexborderlistfromgrid.hh
+++ b/dumux/linear/vertexborderlistfromgrid.hh
@@ -81,7 +81,7 @@ public:
     void gather(MessageBufferImp &buff, const EntityType &e) const
     {
         buff.write(gridView_.comm().rank());
-        buff.write(map_.map(e));
+        buff.write(static_cast<int>(map_.map(e)));
     }
 
     template<class MessageBufferImp, class EntityType>