Climate models show a robust negative feedback in the midlatitudes, coincident with an increase in cloud liquid in the mixed-phase region of the control climate. This "mixed-phase feedback" is normally attributed to a feedback caused by a phase change feedback (ice to liquid). Here we use an aquaplanet configuration to investigate this in more detail. We use high-frequency instantaneous diagnostics and composite them in ascending and descending regimes. We find that a large fraction of the increase in cloud liquid water in the mixed-phase region does not significantly contribute to the radiative feedback due to a masking effect of the ice cloud above. Using some simple arguments and approximate calculations, we estimate that about one third of the total shortwave negative radiative feedback is driven by a phase change feedback, whereas the rest of the feedback is driven by changes in ice and warm liquid clouds.