URL Filter adds automaticly to Bayesian

Is it a bug or a Feature?
If URL-Filter recognizes spam, all URLs are thrown in the {spam_filter_bayesian_tokens} table.
If I use one of these URLs later on, I get a SPAM-message.
Reason:
In function spam_filter_url_spam_filter() the table {spam_filter_bayesian_tokens} is checked and raises an spam-detect.

What can I do (besides to change the code I already done for me) ?