Communication campaigns often highlight environmental progress to encourage further pro-environmental behaviour. Consequently, the drop in carbon emissions caused by the COVID-19 restrictions has been framed as a positive environmental outcome of the pandemic. We conducted an experimental study with a US-representative sample (N = 500) to show that raising awareness of emissions reduction has the contrary effect: an increase in moral self-concept facilitated a negative spillover, namely, it reduced climate-friendly behavioural intentions. Normative influence was able to prevent this negative spillover (...) because activating environmental norms inhibited compensatory feelings. Besides, awareness of recent emissions reduction was less likely to increase the moral self-concept of participants with a strong environmental self-identity. Our findings demonstrate that environmental progress increases moral self-concept which, in turn, could cause a negative spillover (i.e., reduce climate-friendly low-carbon behaviour and increase climate-harmful high-carbon behaviour). Normative influences and environmental self-identity can inhibit this negative spillover. (shrink)