Apparatuses, methods, and systems are disclosed for indicating the IMS capability for EPS fallback. One apparatus in a mobile communication network includes a processor and a transceiver that transmits to an IMS network entity a first SIP message comprising a request for establishing a data session, where the first SIP message contains a first contact header field. The transceiver receives a second SIP message from the IMS network entity for establishing the data session, where the second SIP message contains an indicator. The processor determines an IMS network capability from a combination of the first contact header field and the indicator.