An apparatus configured to transmit a PDCP status report comprising: a PDCP, Packet Data Convergence Protocol, entity at a transmitting side; an upper layer located above the PDCP entity in a radio interface protocol stack; and a lower layer located below the PDCP entity in the radio interface protocol stack, wherein the PDCP entity at the transmitting side is configured to perform the steps of, processing PDCP data units (S110) received from the lower layer after a PDCP re-establishment is requested from the upper layer; compiling (S120-S150, S170) a PDCP status report by, if there is at least one out-of-sequence PDCP SDU, Service Data Unit, stored, setting an FMS, First Missing Sequence number, field to a PDCP sequence number of a first missing PDCP SDU, Service Data Unit, determining a total number of missing PDCP SDUs, if the total number of missing PDCP SDUs is one or less, refraining from including a bitmap field in the PDCP Status report, if the total number of missing PDCP SDUs exceeds one, allocating a bitmap field of length in bits equal to the number of PDCP SNs from and not including the first missing PDCP SDU up to and including the last out-of-sequence PDCP SDUs, rounded up to the next multiple of 8, indicating a '0' in corresponding positions of the bitmap field for all PDCP SD Us that have not been received as indicated by the lower layer, and indicating a '1' in corresponding positions of the bitmap field for all other PDCP SDUs; and sending (S160), to the lower layer, the PDCP status report as a PDCP PDU, Protocol Data Unit, for transmission; wherein the lower layer is a Radio Link Control, RLC, layer. a PDCP, Packet Data Convergence Protocol, entity at a transmitting side; an upper layer located above the PDCP entity in a radio interface protocol stack; and a lower layer located below the PDCP entity in the radio interface protocol stack, wherein the PDCP entity at the transmitting side is configured to perform the steps of, processing PDCP data units (S110) received from the lower layer after a PDCP re-establishment is requested from the upper layer; compiling (S120-S150, S170) a PDCP status report by, if there is at least one out-of-sequence PDCP SDU, Service Data Unit, stored, setting an FMS, First Missing Sequence number, field to a PDCP sequence number of a first missing PDCP SDU, Service Data Unit, determining a total number of missing PDCP SDUs, if the total number of missing PDCP SDUs is one or less, refraining from including a bitmap field in the PDCP Status report, if the total number of missing PDCP SDUs exceeds one, allocating a bitmap field of length in bits equal to the number of PDCP SNs from and not including the first missing PDCP SDU up to and including the last out-of-sequence PDCP SDUs, rounded up to the next multiple of 8, indicating a '0' in corresponding positions of the bitmap field for all PDCP SD Us that have not been received as indicated by the lower layer, and indicating a '1' in corresponding positions of the bitmap field for all other PDCP SDUs; and sending (S160), to the lower layer, the PDCP status report as a PDCP PDU, Protocol Data Unit, for transmission; wherein the lower layer is a Radio Link Control, RLC, layer. <EOS>