diff --git a/src/simulation.cpp b/src/simulation.cpp
index fcb115849..82fce7c22 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -409,7 +409,7 @@ void finalize_batch()
   }
 
   if(settings::surf_mcpl_write && simulation::current_batch == settings::n_batches){
-    auto filename = settings::path_output + ".mcpl";
+    auto filename = settings::path_output + "surface_source.mcpl";
     write_mcpl_source_point(filename.c_str(), true);
   }