diff --git a/wis2box-management/wis2box/data/cap_message.py b/wis2box-management/wis2box/data/cap_message.py
index a64526d17..55153a6dc 100644
--- a/wis2box-management/wis2box/data/cap_message.py
+++ b/wis2box-management/wis2box/data/cap_message.py
@@ -62,8 +62,7 @@ def transform(self, input_data: Union[Path, bytes],
         :returns: `bool` of result
         """
 
-        suffix = filename.split('.')[-1]
-        rmk = filename.split('.')[0]
+        [rmk, suffix] = filename.rsplit('.', 1)
         input_bytes = self.as_bytes(input_data)
 
         # get the sent date from the CAP XML