diff --git a/src/bias/MetaD.cpp b/src/bias/MetaD.cpp
index f147ba764a867a8e645d6ed2bfd84056e3cd0a0a..bfa9b8205cddd964d77c76f9ade543a30aaa8c11 100644
--- a/src/bias/MetaD.cpp
+++ b/src/bias/MetaD.cpp
@@ -875,6 +875,7 @@ last_step_warn_grid(0)
       if(r>0) gridfilename_="/dev/null";
       gridfile_.enforceSuffix("");
     }
+    if(mw_n_>1) gridfile_.enforceSuffix("");
     gridfile_.open(gridfilename_);
   }