Have you ever been trapped by a web page, unable to use the back button to get back to the site you were previously browsing, powerless to do anything but sigh and sacrifice the whole browser tab? Turns out that you may have been the victim of “back-button hijacking,” a practice that Google is cracking down on starting on June 15.

As defined by Google, back-button hijacking occurs “when a site interferes with a user’s browser navigation and prevents them from using their back button to immediately get back to the page they came from.”

This navigational interference can present itself in multiple ways, like locking a user onto their current webpage, presenting unsolicited ads or sending users to completely new pages instead of their intended destination.

Now, Google is adding back-button hijacking to the list of malicious practices covered by its spam policies. According to the company, these practices lead to “a negative and deceptive user experience or compromised user security or privacy.” That means the search giant is classifying the practice as being as offensive as unwanted software executables and malware.

While Google instated its new rules on Tuesday, it won’t start punishing offenders until June 15. According to the company’s blog post, this two-month window has been designated to give website owners enough time to make the necessary changes. This entails removing scripts or techniques that insert or replace webpages in someone’s browser history.

Google will also penalize websites that unintentionally engage in back-button hijacking caused by third-party software on the site.

Websites that don’t make the changes by the deadline could be subject to manual spam actions or to automatically lowered rankings in search engine results. Once a manual spam action has been taken against a website, it can only be removed by fixing the offense and submitting the site for review.

A Google representative did not immediately respond to a request for further comment.