Improving students' views of experimental physics is often an important goal of undergraduate physics laboratory courses. However, traditional lab courses typically include highly guided activities that often do not require or encourage students to engage in the authentic process of experimental physics. Alternatively, open-ended activities in lab courses can provide students with a more authentic learning experience. Here, we investigate the impact of open-ended activities in lab courses on students' views of experimental physics, as measured by the Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS), and concluded that the inclusion of some open-ended activities is associated with more expert-like post-instruction responses relative to the courses that include only traditional guided activities, and the effect is larger for students with low pre-instruction scores. We also found that the number of weeks spent on open-ended activities is not associated with pre-to-post instruction gain in E-CLASS scores.