Fix typo in atom
diff --git a/src/mochiweb_headers.erl b/src/mochiweb_headers.erl
index 457758f..0276aee 100644
--- a/src/mochiweb_headers.erl
+++ b/src/mochiweb_headers.erl
@@ -242,7 +242,7 @@
 reversed_tokens([C | Rest], Token, Acc) ->
     reversed_tokens(Rest, [C | Token], Acc);
 reversed_tokens(_, _, _) ->
-    undefeined.
+    undefined.
 
 extract_quoted_string([], _Acc) ->
     undefined;