Most people pay their taxes most of the time, even if the expected disutility from enforcement is too low to deter tax evasion. One potential reason is tax morale and, more specifically, rule following. In a lab experiment, we show that the willingness to pay taxes just because participants are told they are supposed to pay is indeed pronounced. Yet compliance is reduced if participants learn that income is heterogeneous. The effect is driven by participants with the lowest income. The reduction obtains irrespective of the tax regime. If the tax is proportional to income, or progressive, participants become more skeptical about the willingness of participants with high income to comply.