People’s belief that one or more environmentally friendly items that are added to a set of conventional items can reduce the total environmental impact of these items (the negative footprint illusion) could lead to unwanted environmental consequences. An averaging bias seems to underpin this illusion: people make their estimates based on the average of the environmental impact produced by the items rather than the accumulated sum. We report four studies that used various priming manipulations to explore whether people’s preoccupation to think in terms of an average can be eliminated by fostering a summative mindset. The results demonstrate that participants avoid succumbing to the negative footprint illusion when the critical judgment task is preceded by tasks that engender a summation judgment. Our evidence indicates that the negative footprint illusion can be tempered when a primed concept (summation) is used adaptively on subsequent judgments, thereby correcting for bias in environmental judgments.