BUG: File mode specification error and browse-url-browser-function setting

Hi There is a bug when assigning a list of pairs to browse-url-browser-function and trying to open an html file. I just recently changed its value from a function which according to the documentation is possible. I get the following error: Loading psgml-html... Loading psgml-html...done File mode specification error: (wrong-type-argument symbolp (("^mailto:" . browse-url-mail) ("." . browse-url-netscape))) Loading psgml-parse... Loading psgml-parse...done Any hints ? Ciao Volker