How are incumbent workers impacted by minimum wage increases? Is labour market concentration an important moderating factor? We address these questions by presenting a new model, drawing on comprehensive employer-employee matched panel data from Portugal, and considering individual mandated wage rises from both national and collectively bargained minimum wages. We find that employment protection plays a key role in these effects: workers under permanent contracts are almost completely insulated from the exit hazards associated with wage bites while workers in temporary (fixed-term) contracts are exposed to these hazards. Labour concentration can significantly reduce negative effects on temporary workers, by up to 60\%. A model of monopsonistic competition with firing costs rationalises these patterns.