Union responses to the liberalization of the political economy are often portrayed as either beating the same drum for decades or retreating into the defence of an increasingly small group of core workers. This article argues otherwise. A longitudinal ideational analysis of collective bargaining documents issued between 1976 and 2021 by the Netherlands Trade Union Confederation (FNV) shows that the Federation has gradually adapted its Keynesian-inspired interests to a more market-oriented understanding of the labor market, wages, and employment, legitimized by Third Way ideology in the 1990s. During the 2010s the union returns to Keynesian thinking. The findings suggest that the ideological conversion of the trade union movement may have been more significant than currently realized in explaining the liberalization of the labor market.