To study how local bargaining institutions affect within-job gender wage gaps, we exploit the fact that most Swedish firms tend to have one collective agreement covering all their blue-collar workers. This implies that workers performing the same tasks in different firms are covered by different types of agreements. Our results show that gender pay gaps are smaller when agreements guarantee a yearly minimum pay raise for each worker. The patterns also hold within firms as gender wage gaps in other occupations are uncorrelated with blue-collar rigidities. Bargaining constraints affect gender equality more in female-underrepresented settings and in low-productive firms.