diff --git a/letsencrypt/cli.py b/letsencrypt/cli.py
index 2aedeea8f..ed452b5e6 100644
--- a/letsencrypt/cli.py
+++ b/letsencrypt/cli.py
@@ -352,7 +352,7 @@ def diagnose_configurator_problem(cfg_type, requested, plugins):
         else:
             msg = ("The {0} plugin is not working; there may be problems with "
                    "your existing configuration.\nThe error was: {1}"
-                   .format(requested, plugins[requested].problem))
+                   .format(requested, `plugins[requested].problem`))
     elif cfg_type == "installer":
         if os.path.exists("/etc/debian_version"):
             # Debian... installers are at least possible