diff --git a/include/osmocom/gsm/protocol/gsm_08_58.h b/include/osmocom/gsm/protocol/gsm_08_58.h
index 0a44db90c..ec9ebe715 100644
--- a/include/osmocom/gsm/protocol/gsm_08_58.h
+++ b/include/osmocom/gsm/protocol/gsm_08_58.h
@@ -369,6 +369,7 @@ enum abis_rsl_ie {
 	RSL_IE_OSMO_TRAINING_SEQUENCE	= 0x61,
 	RSL_IE_OSMO_TEMP_OVP_ACCH_CAP	= 0x62,
 	RSL_IE_OSMO_OSMUX_CID		= 0x63,
+	RSL_IE_OSMO_ABS_FRAME_NUMBER	= 0x64, /* uint32_t fn in network byte order */
 
 	/* ip.access */
 	RSL_IE_IPAC_SRTP_CONFIG	= 0xe0,
diff --git a/src/gsm/rsl.c b/src/gsm/rsl.c
index fbba982ab..53eb98341 100644
--- a/src/gsm/rsl.c
+++ b/src/gsm/rsl.c
@@ -126,6 +126,7 @@ const struct tlv_definition rsl_att_tlvdef = {
 		[RSL_IE_OSMO_TRAINING_SEQUENCE]	= { TLV_TYPE_TLV },
 		[RSL_IE_OSMO_TEMP_OVP_ACCH_CAP]	= { TLV_TYPE_TLV },
 		[RSL_IE_OSMO_OSMUX_CID]		= { TLV_TYPE_TLV },
+		[RSL_IE_OSMO_ABS_FRAME_NUMBER]	= { TLV_TYPE_TLV }, /* uint32_t fn in network byte order */
 		[RSL_IE_IPAC_SRTP_CONFIG]	= { TLV_TYPE_TLV },
 		[RSL_IE_IPAC_PROXY_UDP]		= { TLV_TYPE_FIXED, 2 },
 		[RSL_IE_IPAC_BSCMPL_TOUT]	= { TLV_TYPE_TV },