diff --git a/webssh/settings.py b/webssh/settings.py
index cf557d7..2950918 100644
--- a/webssh/settings.py
+++ b/webssh/settings.py
@@ -193,4 +193,4 @@ def get_font_filename(font, font_dir):
 
 def check_encoding_setting(encoding):
     if encoding and not is_valid_encoding(encoding):
-        raise ValueError('Unknown character encoding.')
+        raise ValueError('Unknown character encoding {!r}.'.format(encoding))