diff --git a/letsencrypt-apache/letsencrypt_apache/tls_sni_01.py b/letsencrypt-apache/letsencrypt_apache/tls_sni_01.py
index d78910149..671686433 100644
--- a/letsencrypt-apache/letsencrypt_apache/tls_sni_01.py
+++ b/letsencrypt-apache/letsencrypt_apache/tls_sni_01.py
@@ -144,8 +144,8 @@ class ApacheTlsSni01(common.TLSSNI01):
         if len(self.configurator.parser.find_dir(
                 parser.case_i("Include"), self.challenge_conf)) == 0:
             # print "Including challenge virtual host(s)"
-            logger.debug("Adding Include {0} to {1}".format(
-                            self.challenge_conf, parser.get_aug_path(main_config)))
+            logger.debug("Adding Include %s to %s",
+                          self.challenge_conf, parser.get_aug_path(main_config))
             self.configurator.parser.add_dir(
                 parser.get_aug_path(main_config),
                 "Include", self.challenge_conf)