diff --git a/lib/include/srslte/asn1/liblte_mme.h b/lib/include/srslte/asn1/liblte_mme.h
index 15799f7ca..977f309ce 100644
--- a/lib/include/srslte/asn1/liblte_mme.h
+++ b/lib/include/srslte/asn1/liblte_mme.h
@@ -2721,6 +2721,10 @@ typedef struct{
 // Functions
 LIBLTE_ERROR_ENUM liblte_mme_pack_attach_request_msg(LIBLTE_MME_ATTACH_REQUEST_MSG_STRUCT *attach_req,
                                                      LIBLTE_BYTE_MSG_STRUCT               *msg);
+LIBLTE_ERROR_ENUM liblte_mme_pack_attach_request_msg(LIBLTE_MME_ATTACH_REQUEST_MSG_STRUCT *attach_req,
+                                                     uint8                                 sec_hdr_type,
+                                                     uint32                                count,
+                                                     LIBLTE_BYTE_MSG_STRUCT               *msg);
 LIBLTE_ERROR_ENUM liblte_mme_unpack_attach_request_msg(LIBLTE_BYTE_MSG_STRUCT               *msg,
                                                        LIBLTE_MME_ATTACH_REQUEST_MSG_STRUCT *attach_req);
 
diff --git a/lib/src/asn1/liblte_mme.cc b/lib/src/asn1/liblte_mme.cc
index 4447b001f..215ffd838 100644
--- a/lib/src/asn1/liblte_mme.cc
+++ b/lib/src/asn1/liblte_mme.cc
@@ -1411,9 +1411,9 @@ LIBLTE_ERROR_ENUM liblte_mme_pack_eps_mobile_id_ie(LIBLTE_MME_EPS_MOBILE_ID_STRU
                 **ie_ptr  = (((eps_mobile_id->guti.mnc/10) % 10) << 4) | ((eps_mobile_id->guti.mnc/100) % 10);
                 *ie_ptr  += 1;
             }
-            **ie_ptr  = (eps_mobile_id->guti.mme_group_id >> 8) & 0x0F;
+            **ie_ptr  = (eps_mobile_id->guti.mme_group_id >> 8) & 0xFF;
             *ie_ptr  += 1;
-            **ie_ptr  = eps_mobile_id->guti.mme_group_id & 0x0F;
+            **ie_ptr  = eps_mobile_id->guti.mme_group_id & 0xFF;
             *ie_ptr  += 1;
             **ie_ptr  = eps_mobile_id->guti.mme_code;
             *ie_ptr  += 1;
@@ -5518,6 +5518,14 @@ LIBLTE_ERROR_ENUM liblte_mme_unpack_attach_reject_msg(LIBLTE_BYTE_MSG_STRUCT
 *********************************************************************/
 LIBLTE_ERROR_ENUM liblte_mme_pack_attach_request_msg(LIBLTE_MME_ATTACH_REQUEST_MSG_STRUCT *attach_req,
                                                      LIBLTE_BYTE_MSG_STRUCT               *msg)
+{
+    return liblte_mme_pack_attach_request_msg(attach_req, LIBLTE_MME_SECURITY_HDR_TYPE_PLAIN_NAS, 0, msg);
+}
+
+LIBLTE_ERROR_ENUM liblte_mme_pack_attach_request_msg(LIBLTE_MME_ATTACH_REQUEST_MSG_STRUCT *attach_req,
+                                                     uint8                                 sec_hdr_type,
+                                                     uint32                                count,
+                                                     LIBLTE_BYTE_MSG_STRUCT               *msg)
 {
     LIBLTE_ERROR_ENUM  err     = LIBLTE_ERROR_INVALID_INPUTS;
     uint8             *msg_ptr = msg->msg;
@@ -5525,6 +5533,20 @@ LIBLTE_ERROR_ENUM liblte_mme_pack_attach_request_msg(LIBLTE_MME_ATTACH_REQUEST_M
     if(attach_req != NULL &&
        msg        != NULL)
     {
+        if(LIBLTE_MME_SECURITY_HDR_TYPE_PLAIN_NAS != sec_hdr_type)
+        {
+            // Protocol Discriminator and Security Header Type
+            *msg_ptr = (sec_hdr_type << 4) | (LIBLTE_MME_PD_EPS_MOBILITY_MANAGEMENT);
+            msg_ptr++;
+
+            // MAC will be filled in later
+            msg_ptr += 4;
+
+            // Sequence Number
+            *msg_ptr = count & 0xFF;
+            msg_ptr++;
+        }
+
         // Protocol Discriminator and Security Header Type
         *msg_ptr = (LIBLTE_MME_SECURITY_HDR_TYPE_PLAIN_NAS << 4) | (LIBLTE_MME_PD_EPS_MOBILITY_MANAGEMENT);
         msg_ptr++;