diff --git a/srsepc/hdr/mme/s1ap.h b/srsepc/hdr/mme/s1ap.h
index 3f9f035e0..311a65784 100644
--- a/srsepc/hdr/mme/s1ap.h
+++ b/srsepc/hdr/mme/s1ap.h
@@ -72,7 +72,7 @@ public:
   bool handle_initiating_message(LIBLTE_S1AP_INITIATINGMESSAGE_STRUCT *msg, struct sctp_sndrcvinfo *enb_sri);
   bool handle_successful_outcome(LIBLTE_S1AP_SUCCESSFULOUTCOME_STRUCT *msg);
 
-  void activate_eps_bearer(uint32_t mme_s1ap_id, uint8_t ebi);
+  void activate_eps_bearer(uint64_t imsi, uint8_t ebi);
 
   void print_enb_ctx_info(const std::string &prefix, const enb_ctx_t &enb_ctx);
 
diff --git a/srsepc/src/mme/mme_gtpc.cc b/srsepc/src/mme/mme_gtpc.cc
index fff721978..ff603e14d 100644
--- a/srsepc/src/mme/mme_gtpc.cc
+++ b/srsepc/src/mme/mme_gtpc.cc
@@ -288,16 +288,16 @@ void
 mme_gtpc::handle_modify_bearer_response(srslte::gtpc_pdu *mb_resp_pdu)
 {
   uint32_t mme_ctrl_teid = mb_resp_pdu->header.teid;
-  std::map<uint32_t,uint32_t>::iterator mme_s1ap_id_it = m_teid_to_mme_s1ap_id.find(mme_ctrl_teid);
-  if(mme_s1ap_id_it == m_teid_to_mme_s1ap_id.end())
+  std::map<uint32_t,uint64_t>::iterator imsi_it = m_mme_ctr_teid_to_imsi.find(mme_ctrl_teid);
+  if(imsi_it == m_mme_ctr_teid_to_imsi.end())
   {
-    m_mme_gtpc_log->error("Could not find MME S1AP Id from control TEID\n");
+    m_mme_gtpc_log->error("Could not find IMSI from control TEID\n");
     return;
   }
 
   uint8_t ebi = mb_resp_pdu->choice.modify_bearer_response.eps_bearer_context_modified.ebi;
   m_mme_gtpc_log->debug("Activating EPS bearer with id %d\n", ebi);
-  m_s1ap->activate_eps_bearer(mme_s1ap_id_it->second,ebi);
+  m_s1ap->activate_eps_bearer(imsi_it->second,ebi);
 
   return;
 }
diff --git a/srsepc/src/mme/s1ap.cc b/srsepc/src/mme/s1ap.cc
index 6e301b9ae..a54096114 100644
--- a/srsepc/src/mme/s1ap.cc
+++ b/srsepc/src/mme/s1ap.cc
@@ -501,23 +501,31 @@ s1ap::delete_ues_ecm_ctx_in_enb(uint16_t enb_id)
 
 //UE Bearer Managment
 void
-s1ap::activate_eps_bearer(uint32_t mme_s1ap_id, uint8_t ebi)
+s1ap::activate_eps_bearer(uint64_t imsi, uint8_t ebi)
 {
-  std::map<uint32_t,ue_ecm_ctx_t*>::iterator ue_ctx_it = m_mme_ue_s1ap_id_to_ue_ecm_ctx.find(mme_s1ap_id);
-  if(ue_ctx_it == m_mme_ue_s1ap_id_to_ue_ecm_ctx.end())
+  std::map<uint64_t,ue_emm_ctx_t*>::iterator emm_ctx_it = m_imsi_to_ue_emm_ctx.find(imsi);
+  if(emm_ctx_it == m_imsi_to_ue_emm_ctx.end())
   {
-    m_s1ap_log->error("Could not find UE context\n");
+      m_s1ap_log->error("Could not find UE EMM context\n");
+      return;
+  }
+  uint32_t mme_ue_s1ap_id = emm_ctx_it->second->mme_ue_s1ap_id;
+  std::map<uint32_t,ue_ecm_ctx_t*>::iterator ecm_ctx_it = m_mme_ue_s1ap_id_to_ue_ecm_ctx.find(mme_s1ap_id);
+  if(ecm_ctx_it == m_mme_ue_s1ap_id_to_ue_ecm_ctx.end())
+  {
+    m_s1ap_log->error("Could not find UE ECM context\n");
     return;
   }
-  ue_ecm_ctx_t * ue_ctx = ue_ctx_it->second;
-  if (ue_ctx->erabs_ctx[ebi].state != ERAB_CTX_SETUP)
+
+  ue_ecm_ctx_t * ecm_ctx = ue_ctx_it->second;
+  if (ecm_ctx->erabs_ctx[ebi].state != ERAB_CTX_SETUP)
   {
     m_s1ap_log->error("EPS Bearer could not be activated. MME S1AP Id %d, EPS Bearer id %d, state %d\n",mme_s1ap_id,ebi,ue_ctx->erabs_ctx[ebi].state);
     m_s1ap_log->console("EPS Bearer could not be activated. MME S1AP Id %d, EPS Bearer id %d\n",mme_s1ap_id,ebi,ue_ctx->erabs_ctx[ebi].state);
     return;
   }
 
-  ue_ctx->erabs_ctx[ebi].state = ERAB_ACTIVE;
+  ecm_ctx->erabs_ctx[ebi].state = ERAB_ACTIVE;
   m_s1ap_log->info("Activated EPS Bearer\n");
   return;
 }