The incubation period is regarded as an important stage in creative problem solving. The incubation effect manifests itself in the enhanced problem-solving performance after taking a break. Forgetting fixation hypothesis states that incubation provides a problem solver with an opportunity to eliminate inappropriate ideas (mental sets) and therefore to come up with a correct solution. We explored in two studies whether forgetting is an actual mechanism of the incubation period (i.e. whether the traces of inappropriate fixations in memory become weaker as a consequence of incubation). In Study 1 we employed the Alternative Uses Task (AUT) and fixed part of the participants on several most common ways of using an object. We checked then whether incubation helped to forget our fixations. We found the incubation effect (i.e. a greater fluency at the second attempt) only when participants were previously fixated. However, we also found that the incubation didn’t influence the number of fixations. Thus, we failed to find the evidence for forgetting fixation during the incubation period. In Study 2 we used anagrams with two possible solutions and fixed the participant on one of them. Then we used the Lexical Decision Task (LDT) to examine whether these fixations would become weaker as a result of the incubation period. No differences were found between the incubation and no-incubation groups in their response latencies for fixation words. Our results indicate that while the assumption that the function of an incubation period is in overcoming inappropriate mental sets seems to be true, the forgetting fixation theory provides an inaccurate account of underlying mechanisms.