diff --git a/bin/ffx.py b/bin/ffx.py
index b9ab471..9f820be 100755
--- a/bin/ffx.py
+++ b/bin/ffx.py
@@ -60,7 +60,7 @@ if 'vp9' in sys.argv:
     targetFormat = 'vp9'
 
 
-qualities = [DEFAULT_QUALITY]
+qualities = [str(DEFAULT_QUALITY)]
 qualitiesTokens = [q for q in sys.argv if q.startswith('q=')]
 if qualitiesTokens:
   qualitiesString = qualitiesTokens[0].split('=')[1]