diff --git a/src/Fortran/abstract_load_balancer.f90 b/src/Fortran/abstract_load_balancer.f90
index bf4774a..b596ac5 100644
--- a/src/Fortran/abstract_load_balancer.f90
+++ b/src/Fortran/abstract_load_balancer.f90
@@ -30,7 +30,7 @@ module SLB4MPI_abstract_load_balancer_m
     procedure :: default_initialize
   end type
 
-  interface
+  abstract interface
 
     !>
     !> @brief initialize load balancer