We discuss the limit of validity of the procedure which is used to predict the End Of Life (EOL) performances of a solar cell in space. This procedure consists to measure the performances of a cell after it has been irradiated at the EOL fluence during a time very short compared to the lifetime in space, i.e. with a considerably larger flux. We demonstrate that this procedure is not valid when the defects created by the irradiation anneal during the irradiation. This is for instance the case of GaInP cells, which are at the heart of the modern high efficiency multijunction space solar cells. To illustrate the effect of injection annealing during irradiation, we model the time dependence of the concentration of the irradiation induced defects in GaInP in different practical situations.