diff --git a/warcprox/dedup.py b/warcprox/dedup.py
index 43286d7..167fdba 100644
--- a/warcprox/dedup.py
+++ b/warcprox/dedup.py
@@ -437,7 +437,7 @@ class BatchTroughLoader(warcprox.BaseBatchPostfetchProcessor):
             else:
                 if hash_plus_url in hash_plus_urls:
                     self.logger.debug(
-                        'discarding duplicate and setting do_not_archive for %, hash %'.format(
+                        'discarding duplicate and setting do_not_archive for %s, hash %s'.format(
                             recorded_url.url, payload_hash))
                     recorded_url.do_not_archive = True
                 discards.append(payload_hash)