diff --git a/youtube_dl/extractor/audiomack.py b/youtube_dl/extractor/audiomack.py
index 693ba22c6..3eed91279 100644
--- a/youtube_dl/extractor/audiomack.py
+++ b/youtube_dl/extractor/audiomack.py
@@ -56,7 +56,7 @@ class AudiomackIE(InfoExtractor):
 
         # API is inconsistent with errors
         if 'url' not in api_response or not api_response['url'] or 'error' in api_response:
-            raise ExtractorError('Invalid url %s', url)
+            raise ExtractorError('Invalid url %s' % url)
 
         # Audiomack wraps a lot of soundcloud tracks in their branded wrapper
         # if so, pass the work off to the soundcloud extractor