diff --git a/garminexport/garminclient.py b/garminexport/garminclient.py
index ac8ea87..b3cde19 100755
--- a/garminexport/garminclient.py
+++ b/garminexport/garminclient.py
@@ -308,7 +308,11 @@ class GarminClient(object):
         # and is the one used when exporting through the Garmin
         # Connect web page.
         #response = self.session.get("https://connect.garmin.com/proxy/activity-service-1.1/gpx/activity/{}?full=true".format(activity_id))
-        if response.status_code == 404:
+        
+        # A 404 (Not Found) or 204 (No Content) response are both indicators
+        # of a gpx file not being available for the activity. It may, for
+        # example be a manually entered activity without any device data.
+        if response.status_code in (404, 204):
             return None
         if response.status_code != 200:
             raise Exception(u"failed to fetch GPX for activity {}: {}\n{}".format(