diff --git a/src/lipase/catalog.py b/src/lipase/catalog.py
index 5a58304..6033e8c 100644
--- a/src/lipase/catalog.py
+++ b/src/lipase/catalog.py
@@ -64,13 +64,13 @@ class Sequence(object):
         summary = self.mmm['Summary']
         num_frames = int(summary['Frames'])
         # handle the case where the recording has been cancelled by the user and therefore the actual number of frames is lower than initially planned
-        num_existing_frames = 0
+        num_existing_frames = num_frames
         for frame_index in range(num_frames):
             frame_key_key = 'FrameKey-%d-0-0' % (frame_index)
-            if not frame_key_key in self.mmm.keys():
+            if frame_key_key not in self.mmm.keys():
+                # print('missing frame : %s' % frame_key_key)
                 num_existing_frames = frame_index
                 break
-            
         return num_existing_frames
 
     @property