A method of enhancing IP packet forwarding feature support after interworking is proposed. When a PDU session in 5GS is transferred to a PDN connection in EPS, the UE shall assume the feature is supported after inter-system change from 5GS to EPS. When a PDN connection is established in EPS, the network indicated that the feature is not supported, and the network provided 5GSM parameters for ESM/5GSM interworking for this PDN connection, then UE shall assume the feature is supported after inter-system change from EPS to 5GS, the UE shall also assume the feature is supported after inter-system change from 5GS back to EPS. The IP packet forwarding features include PS data off and local IP address in TFT.