diff --git a/gallery_dl/output.py b/gallery_dl/output.py
index 35185452..bd5d9594 100644
--- a/gallery_dl/output.py
+++ b/gallery_dl/output.py
@@ -105,6 +105,7 @@ class LoggerAdapterActions():
         self.error = functools.partial(self.log, logging.ERROR)
 
     def log(self, level, msg, *args, **kwargs):
+        msg = str(msg)
         if args:
             msg = msg % args