diff --git a/Convert_Matlab/inst_eddies_v6.py b/Convert_Matlab/inst_eddies_v6.py
index 4d5180f1f6f6ca9488bbdf6fbecbdfd5e779b29c..5857b835a9257716af6166bc051ab66ef5e1a66b 100755
--- a/Convert_Matlab/inst_eddies_v6.py
+++ b/Convert_Matlab/inst_eddies_v6.py
@@ -174,8 +174,11 @@ while True:
 nml = f90nml.Namelist()
 nml["grid_nml"] = dict(corner_deg = [matlab_data["X"][0], matlab_data["Y"][0]],
                        nlon = matlab_data["X"].size,
-                       nlat = matlab_data["Y"].size)
+                       nlat = matlab_data["Y"].size,
+                       step_deg = [matlab_data["X"][1] - matlab_data["X"][0],
+                                   matlab_data["Y"][1] - matlab_data["Y"][0]])
 
 for f in factories:
-    nml.write(path.join(f["SHP_coll"], "grid_nml.txt"), force = True)
+    file = path.join(f["SHP_coll"], "grid_nml.txt")
+    nml.write(file, force = True)
     for k, v in f["writers"].items(): v.close()