Many recent electoral events have been characterised by false claims which, despite abundant fact-checking, were often widely believed. This led to much talk about ’post-truth’ politics. An extensive literature confirms that political misperceptions are resistant to correction. But how far does that tendency stretch? And how do post-truth surroundings affect the way people respond to expert information that challenges political beliefs? We conducted a representative survey experiment in Britain (N=2900) concerning common misperceptions – both liberal and conservative – about immigration. We follow the classic setup of misperception-correction studies but add a twist: First, we identify false beliefs about immigration and provide expert information countering one of those false beliefs. Second, we approximate ‘real world’ conditions, where expert information is rarely the final word: We show respondents a comment from a blogger or a professor giving one of three reasons to ‘take these statistics with a big pinch of salt’. Finally, we ask respondents to re-assess the false claims and answer questions explicitly testing for a post-truth mindset. Our results show that fact-checks worked: The expert statement significantly reduced belief in the false fact. However, the post-truth comment worked, too: If the fact-checker did not have the final word – if respondents read a post-truth comment before they re-evaluated the facts – then they kept the false fact on the ’true’ side of our scale.