diff -r 0ee62085ea82 -r 509aefe2f45c src/pyams_media/utility.py
--- a/src/pyams_media/utility.py	Tue May 16 11:16:15 2017 +0200
+++ b/src/pyams_media/utility.py	Wed Jun 07 09:28:15 2017 +0200
@@ -50,7 +50,9 @@
 
     def check_media_conversion(self, media):
         """Check if conversion is needed for given media"""
-        content_type = media.content_type.decode() if media.content_type else None
+        content_type = media.content_type
+        if isinstance(content_type, bytes):
+            content_type = content_type.decode()
         if self.audio_formats and \
            (content_type.startswith('audio/') or (content_type in CUSTOM_AUDIO_TYPES)):
             requested_formats = self.audio_formats