diff --git a/src/l2cap.c b/src/l2cap.c
index 2e260a68c..c4710ef53 100644
--- a/src/l2cap.c
+++ b/src/l2cap.c
@@ -1088,10 +1088,9 @@ uint8_t l2cap_create_ertm_channel(btstack_packet_handler_t channel_packet_handle
         return BTSTACK_MEMORY_ALLOC_FAILED;
     }
 
-#ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
     channel->mode = L2CAP_CHANNEL_MODE_ENHANCED_RETRANSMISSION;
-#endif    
-
+    channel->ertm_mandatory = 1;
+    
     // add to connections list
     btstack_linked_list_add(&l2cap_channels, (btstack_linked_item_t *) channel);
 
@@ -1458,6 +1457,7 @@ void l2cap_accept_ertm_connection(uint16_t local_cid){
 
     // configure L2CAP ERTM
     channel->mode  = L2CAP_CHANNEL_MODE_ENHANCED_RETRANSMISSION;
+    channel->ertm_mandatory = 1;
 
     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
 
diff --git a/src/l2cap.h b/src/l2cap.h
index 5cc9bcd96..fad1d7a23 100644
--- a/src/l2cap.h
+++ b/src/l2cap.h
@@ -180,6 +180,7 @@ typedef struct {
 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
     // l2cap channel mode: basic or enhanced retransmission mode
     l2cap_channel_mode_t mode;
+    uint8_t ertm_mandatory;
 #endif    
 } l2cap_channel_t;