The present invention relates to a method and arrangement for controlling re-transmission in a user equipment supporting uplink spatial multiplexing. The method comprises the steps of detecting an uplink grant on a physical downlink control channel, the uplink grant being valid for at least one transport block; detecting that at least one transport block is disabled, such that no grant is associated with the at least one transport block; and interpreting the at least one disabled transport block as an acknowledgement, ACK, of previous transmission corresponding to said disabled transport block irrespective of which indication is received on the reception status feedback channel for said previous transmission.