diff --git a/ffwrapper.py b/ffwrapper.py
index 48fc85e..7e63905 100644
--- a/ffwrapper.py
+++ b/ffwrapper.py
@@ -66,7 +66,7 @@ def start_ffmpeg(infile: Path, outfile: Path):
 
 
 def set_progress(line: str, dur, pbar):
-    if not line.startswith("out_time_ms="):
+    if not pbar or not line.startswith("out_time_ms="):
         return
     try:
         us = int(line.split('=')[1])