diff --git a/larigira/filters/basic.py b/larigira/filters/basic.py
index 5667d49..135df3c 100644
--- a/larigira/filters/basic.py
+++ b/larigira/filters/basic.py
@@ -66,7 +66,10 @@ def percentwait(songs, context, conf, getdur=get_duration):
 
     if eventduration == 0:
         # must be an error! mutagen support is not always perfect
-        return True, 'mutagen could not calculate length of %s' % uri
+        return (
+            True,
+            ("mutagen could not calculate length of %s" % ",".songs["uris"]),
+        )
     wait = eventduration * (percentwait / 100.0)
     if remaining > wait:
         return False, "remaining %d max allowed %d" % (remaining, wait)