diff --git a/libsrc/general/mpi_interface.hpp b/libsrc/general/mpi_interface.hpp
index 0d9a65fc..423c341b 100644
--- a/libsrc/general/mpi_interface.hpp
+++ b/libsrc/general/mpi_interface.hpp
@@ -15,7 +15,7 @@
 namespace netgen
 {
 
-  extern int id, ntasks;
+  extern DLL_HEADER int id, ntasks;
   
 
 #ifdef PARALLEL