diff --git a/NAERSTADMO.py b/NAERSTADMO.py
index e29026a4c948959fd449bba8415228b9d3e79fff..9855df1f4b4b8ee575688cb689cc9ea2e0e65abd 100644
--- a/NAERSTADMO.py
+++ b/NAERSTADMO.py
@@ -154,7 +154,7 @@ def create_warning_status(start_date):
         else:
             os.rename(
                 f"{tmpfile_path}result_unmasked.nc",
-                f"{tmpfile_path}result{file_date}.nc",
+                f"{tmpfile_path}result_{file_date}.nc",
             )
 
         if file_date > start_date.strftime("%Y-%m-%d"):