type=int makes the argument default to 0

website/routes.py

@@ -126,7 +126,7 @@ def segments():
     except KeyError:
         pass
 
-    start_number = request.args.get('segment', type=int) or resolve_segment_offset()
+    start_number = request.args.get('segment', type=int) if 'segment' in request.args else resolve_segment_offset()
 
     try:
         concatenated_segments = ConcatenatedSegments(start_number=start_number,
@@ -327,4 +327,4 @@ def add_header(response):
 
 @current_app.route('/teapot')
 def teapot():
-    return {'short': True, 'stout': True}, 418
+    return {'short': True, 'stout': True}, 418