diff --git a/wahoomc/osm_maps_functions.py b/wahoomc/osm_maps_functions.py
index 9eec9f15..7be4b8e0 100644
--- a/wahoomc/osm_maps_functions.py
+++ b/wahoomc/osm_maps_functions.py
@@ -494,9 +494,15 @@ def merge_splitted_tiles_with_land_and_sea(self, process_border_countries, conto
 
                     loop += 1
 
+            loop = 0
+            # loop through all land* osm files, merge only if more than one file is involved.
             for land in land_files:
                 cmd.extend(
-                    ['--rx', 'file='+land, '--s', '--m'])
+                    ['--rx', 'file='+land, '--s'])
+                if loop > 0:
+                    cmd.append('--m')
+
+                loop += 1
 
             if contour:
                 for elevation in elevation_files: