diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
index a9d3dbb9c..fc8cecc45 100755
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -646,7 +646,7 @@ class YoutubeDL(object):
                 playlist_results.append(entry_result)
             ie_result['entries'] = playlist_results
 
-            if self.params['concat']:
+            if self.params.get('concat', False):
                 concat = FFmpegConcatPP(self)
                 if concat._get_executable():
                     postprocessors = [concat]