diff --git a/lib/jekyll/configuration.rb b/lib/jekyll/configuration.rb
index ae75034b..a58efd8c 100644
--- a/lib/jekyll/configuration.rb
+++ b/lib/jekyll/configuration.rb
@@ -106,7 +106,7 @@ module Jekyll
       when /\.y(a)?ml/
         YAML.safe_load_file(filename)
       else
-        raise ArgumentError, "No parser for '#{filename}' is available."kk
+        raise ArgumentError, "No parser for '#{filename}' is available. Use a .toml or .y(a)ml file instead."
       end
     end