This paper explores the effects of exposure to AI-generated images on design fixation and divergent thinking in a visual ideation task. Through a between-participants experiment involving 60 participants, the study found that support from an AI image generator during ideation leads to higher fixation on an initial example. Participants who used AI-generated images produced fewer ideas, with less variety and lower originality compared to a baseline condition. Qualitative analysis suggests that the effectiveness of co-ideation with AI depends on participants' approach to prompt creation and their strategies for generating ideas in response to AI suggestions. The study provides empirical evidence for the influence of AI-generated images on design fixation and divergent thinking, highlighting the importance of considering factors that induce design fixation when using AI tools for inspiration. The findings also suggest potential strategies for mitigating design fixation in ideation workflows.This paper explores the effects of exposure to AI-generated images on design fixation and divergent thinking in a visual ideation task. Through a between-participants experiment involving 60 participants, the study found that support from an AI image generator during ideation leads to higher fixation on an initial example. Participants who used AI-generated images produced fewer ideas, with less variety and lower originality compared to a baseline condition. Qualitative analysis suggests that the effectiveness of co-ideation with AI depends on participants' approach to prompt creation and their strategies for generating ideas in response to AI suggestions. The study provides empirical evidence for the influence of AI-generated images on design fixation and divergent thinking, highlighting the importance of considering factors that induce design fixation when using AI tools for inspiration. The findings also suggest potential strategies for mitigating design fixation in ideation workflows.