In a world where exposure to untrustworthy communicators is common, trust has become more important than ever for effective marketing. Nevertheless, we know very little about the long-term consequences of exposure to untrustworthy sources, such bullshitters. This research examines how untrustworthy sources--liars and bullshitters--influence consumer attitudes toward a product. Frankfurt's (1986) "insidious bullshit hypothesis" (i.e., bullshitting is evaluated less negatively than lying but bullshit can be more harmful than are lies) is examined within a traditional sleeper effect--a persuasive influence that increases, rather than decays over time. We obtained a sleeper effect after participants learned that the source of the message was either a liar or a bullshitter. However, compared to the liar source condition, the same message from a bullshitter resulted in more extreme immediate and delayed attitudes that were in line with an otherwise discounted persuasive message (i.e., an advertisement). Interestingly, attitudes returned to control condition levels when a bullshitter was the source of the message, suggesting that knowing an initially discounted message may be potentially accurate/inaccurate (as is true with bullshit, but not lies) does not result in the long-term discounting of that message. We discuss implications for marketing and other contexts of persuasion.