Drawing on frame theory, this paper examines how policy entrepreneurs within the Swedish Trade Union Confederation Landsorganisationen i Sverige (LO) embarked on a campaign to extend an exclusively class-based solidarity frame along gender lines. In the process, LO’s identity was modified. Once the new solidarity frame had been accepted, it was operationalized in the collective bargaining process through the creation of a “women’s pot”—i.e., a wage supplement given to female employees, or female-dominated sectors, to counter gender-based pay discrimination. Nevertheless, the new frame has yet to meet with success in the wage-bargaining arena, as LO faces problems of intra-union coordination in an unfavorable institutional context.