Zuber＇s analysis of the acceleration reaction on a bubble in a concentrated suspension is extended to the case in which the bubble radius changes with time. The analysis is based on a cell model: the bubble is at the centre of a sphere filled with incompressible fluid. The bubble grows and translates, whereas the centre of the outer boundary is at rest; thus the calculations are performed in a frame of zero total volume flux. The predicted force on the bubble in a concentrated suspension agrees, in the dilute limit, with previous results for the force on a single bubble growing in unbounded fluid, and becomes large as the volume fraction of the gas increases.