diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8739097b2..39e56f977 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,6 +40,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - GAP: fix `gap_connect` after `gap_connect_cancel` 
 - HCI: handle start inquiry failure
 - L2CAP: fix create outgoing connection triggered in hci disconnect event callback
+- L2CAP: return unknown mandatory option in config response
 - AVRCP Target: fix notification changed event
 - HFP: Emit Audio Connection Released on SLC Release, e.g. remote power off
 - HFP HF: only emit single event for RING and AG Status updates
diff --git a/src/l2cap.c b/src/l2cap.c
index 7e6c231dc..944f3b136 100644
--- a/src/l2cap.c
+++ b/src/l2cap.c
@@ -1543,7 +1543,7 @@ static bool l2cap_run_for_classic_channel(l2cap_channel_t * channel){
                 }
                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_INVALID){
                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP);
-                    l2cap_send_signaling_packet(channel->con_handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, L2CAP_CONF_RESULT_UNKNOWN_OPTIONS, 0, NULL);
+                    l2cap_send_signaling_packet(channel->con_handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, L2CAP_CONF_RESULT_UNKNOWN_OPTIONS, 1, &channel->unknown_option);
 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
                 } else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_REJECTED){
                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_REJECTED);
@@ -2739,7 +2739,8 @@ static void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, u
 #endif        
         // check for unknown options
         if ((option_hint == 0) && ((option_type < L2CAP_CONFIG_OPTION_TYPE_MAX_TRANSMISSION_UNIT) || (option_type > L2CAP_CONFIG_OPTION_TYPE_EXTENDED_WINDOW_SIZE))){
-            log_info("l2cap cid %u, unknown options", channel->local_cid);
+            log_info("l2cap cid %u, unknown option 0x%02x", channel->local_cid, option_type);
+            channel->unknown_option = option_type;
             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_INVALID);
         }
         pos += length;
@@ -2797,7 +2798,8 @@ static void l2cap_signaling_handle_configure_response(l2cap_channel_t *channel,
 
         // check for unknown options
         if (option_hint == 0 && (option_type < L2CAP_CONFIG_OPTION_TYPE_MAX_TRANSMISSION_UNIT || option_type > L2CAP_CONFIG_OPTION_TYPE_EXTENDED_WINDOW_SIZE)){
-            log_info("l2cap cid %u, unknown options", channel->local_cid);
+            log_info("l2cap cid %u, unknown option 0x%02x", channel->local_cid, option_type);
+            channel->unknown_option = option_type;
             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_INVALID);
         }
 
diff --git a/src/l2cap.h b/src/l2cap.h
index 25a0c17d6..f866827d0 100644
--- a/src/l2cap.h
+++ b/src/l2cap.h
@@ -245,6 +245,8 @@ typedef struct {
 
     uint8_t   reason; // used in decline internal
 
+    uint8_t   unknown_option; // used for ConfigResponse
+
     // LE Data Channels
 
     // incoming SDU