diff --git a/openair2/COMMON/s1ap_messages_def.h b/openair2/COMMON/s1ap_messages_def.h
index 3e41dae2a99b04376a09be5fdcbadb88bc905e5c..554425aff23b10283d1d9447d718072ec99dca02 100644
--- a/openair2/COMMON/s1ap_messages_def.h
+++ b/openair2/COMMON/s1ap_messages_def.h
@@ -3,6 +3,7 @@ MESSAGE_DEF(S1AP_REGISTER_ENB_REQ          , MESSAGE_PRIORITY_MED, s1ap_register
 
 /* S1AP -> eNB application layer messages */
 MESSAGE_DEF(S1AP_REGISTER_ENB_CNF          , MESSAGE_PRIORITY_MED, s1ap_register_enb_cnf_t          , s1ap_register_enb_cnf)
+MESSAGE_DEF(S1AP_DEREGISTERED_ENB_IND      , MESSAGE_PRIORITY_MED, s1ap_deregistered_enb_ind_t      , s1ap_deregistered_enb_ind)
 
 /* RRC -> S1AP messages */
 MESSAGE_DEF(S1AP_NAS_FIRST_REQ             , MESSAGE_PRIORITY_MED, s1ap_nas_first_req_t             , s1ap_nas_first_req)
diff --git a/openair2/COMMON/s1ap_messages_types.h b/openair2/COMMON/s1ap_messages_types.h
index 898f5989eff4e5e671e2a66e61982a9b2d9bab82..911c65ba0e70d60f51c2e1185c11f591ebeecfae 100644
--- a/openair2/COMMON/s1ap_messages_types.h
+++ b/openair2/COMMON/s1ap_messages_types.h
@@ -7,6 +7,7 @@
 #define S1AP_REGISTER_ENB_REQ(mSGpTR)           (mSGpTR)->ittiMsg.s1ap_register_enb_req
 
 #define S1AP_REGISTER_ENB_CNF(mSGpTR)           (mSGpTR)->ittiMsg.s1ap_register_enb_cnf
+#define S1AP_DEREGISTERED_ENB_IND(mSGpTR)       (mSGpTR)->ittiMsg.s1ap_deregistered_enb_ind
 
 #define S1AP_NAS_FIRST_REQ(mSGpTR)              (mSGpTR)->ittiMsg.s1ap_nas_first_req
 #define S1AP_UPLINK_NAS(mSGpTR)                 (mSGpTR)->ittiMsg.s1ap_uplink_nas
@@ -283,9 +284,13 @@ typedef struct s1ap_register_enb_req_s {
 typedef struct s1ap_register_enb_cnf_s {
     /* Nb of MME connected */
     uint8_t          nb_mme;
-
 } s1ap_register_enb_cnf_t;
 
+typedef struct s1ap_deregistered_enb_ind_s {
+    /* Nb of MME connected */
+    uint8_t          nb_mme;
+} s1ap_deregistered_enb_ind_t;
+
 //-------------------------------------------------------------------------------------------//
 // RRC -> S1AP messages