diff --git a/panasonic.py b/panasonic.py
index ce2973d..6e235a4 100755
--- a/panasonic.py
+++ b/panasonic.py
@@ -277,11 +277,12 @@ def downloadMovie(url, outputFileName):
             output.write(chunk)
             if nbiters == 1000:
                 lastTS = getLastTSFromFD(outputFD)
-                delta = lastTS-initialTS    
-                ratio = delta/total
-                length = fstat(outputFD).st_size
-                estimatedLength = ceil(length/ratio)
-                pb.total = estimatedLength
+                if lastTS != None:
+                    delta = lastTS-initialTS    
+                    ratio = delta/total
+                    length = fstat(outputFD).st_size
+                    estimatedLength = ceil(length/ratio)
+                    pb.total = estimatedLength
                 lseek(outputFD, 0, SEEK_END)
                 nbiters = 0
             pb.update(len(chunk))