diff --git a/ffmpeg.py b/ffmpeg.py
index 6e5bcbe..6b5c0ed 100755
--- a/ffmpeg.py
+++ b/ffmpeg.py
@@ -115,11 +115,11 @@ for clip in edit:
         else:
             aid = src_info['audio'][0]['id']
             audio = []
+            audio_map = ['-map', '0:%s,0:0' % aid, '-map', '0:%s,0:1' % vid]
             if clip.get('volume', 1) != 1:
-                audio += [
+                audio_map += [
                     '-filter:a', 'volume=%s' % clip['volume']
                 ]
-            audio_map = ['-map', '0:%s,0:0' % aid, '-map', '0:%s,0:1' % vid]
         cmd = [
             'ffmpeg',
             '-nostats', '-loglevel', 'error',