route withdraws on BGP route-refresh

Hello all, While debugging a route-refresh issue we discovered that when a route-refresh is received, bird, instead of just sending an update containing the exported routes, also withdraws **all known routes** from its peer. In our case, it withdraws the whole FIRT sending multiple BGP updates. Is this the expected behaviour? We are using bird 1.4.5. We believe that the opposite router has trouble processing all those withdrawed routes which leads to other connectivity issues.