diff --git a/src/l2cap.c b/src/l2cap.c
index 770a8eae5..adedf9fb9 100644
--- a/src/l2cap.c
+++ b/src/l2cap.c
@@ -1168,6 +1168,35 @@ uint8_t l2cap_create_channel(btstack_packet_handler_t channel_packet_handler, bd
 
 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
 
+static uint8_t l2cap_ertm_validate_local_config(uint8_t max_transmit, uint16_t retransmission_timeout_ms,
+    uint16_t monitor_timeout_ms, uint8_t num_tx_buffers, uint8_t num_rx_buffers, uint8_t * buffer, uint32_t size){
+    UNUSED(buffer);
+    UNUSED(size);
+
+    uint8_t result = ERROR_CODE_SUCCESS;
+    if (max_transmit < 1){
+        log_error("max_transmit must be >= 1");
+        result = ERROR_CODE_INVALID_HCI_COMMAND_PARAMETERS;
+    }
+    if (retransmission_timeout_ms < 2000){
+        log_error("retransmission_timeout_ms must be >= 2000 ms");
+        result = ERROR_CODE_INVALID_HCI_COMMAND_PARAMETERS;
+    }
+    if (monitor_timeout_ms < 12000){
+        log_error("monitor_timeout_ms must be >= 12000 ms");
+        result = ERROR_CODE_INVALID_HCI_COMMAND_PARAMETERS;
+    }
+    if (num_rx_buffers < 1){
+        log_error("num_rx_buffers must be >= 1");
+        result = ERROR_CODE_INVALID_HCI_COMMAND_PARAMETERS;
+    }
+    if (num_tx_buffers < 1){
+        log_error("num_rx_buffers must be >= 1");
+        result = ERROR_CODE_INVALID_HCI_COMMAND_PARAMETERS;
+    }
+    return result;
+}
+
 static void l2cap_ertm_configure_channel(l2cap_channel_t * channel, int ertm_mandatory, uint8_t max_transmit,
     uint16_t retransmission_timeout_ms, uint16_t monitor_timeout_ms, uint8_t num_tx_buffers, uint8_t num_rx_buffers, uint8_t * buffer, uint32_t size){
 
@@ -1203,6 +1232,10 @@ uint8_t l2cap_create_ertm_channel(btstack_packet_handler_t packet_handler, bd_ad
 
     log_info("L2CAP_CREATE_CHANNEL addr %s psm 0x%x -> local mtu %u", bd_addr_to_str(address), psm, local_mtu);
 
+    // validate local config
+    uint8_t result = l2cap_ertm_validate_local_config(max_transmit, retransmission_timeout_ms, monitor_timeout_ms, num_tx_buffers, num_rx_buffers, buffer, size);
+    if (result) return result;
+
     l2cap_channel_t * channel = l2cap_create_channel_entry(packet_handler, address, BD_ADDR_TYPE_CLASSIC, psm, local_mtu, LEVEL_0);
     if (!channel) {
         return BTSTACK_MEMORY_ALLOC_FAILED;
@@ -1575,16 +1608,20 @@ void l2cap_accept_connection(uint16_t local_cid){
 
 
 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
-void l2cap_accept_ertm_connection(uint16_t local_cid, int ertm_mandatory, uint8_t max_transmit,
+uint8_t l2cap_accept_ertm_connection(uint16_t local_cid, int ertm_mandatory, uint8_t max_transmit,
     uint16_t retransmission_timeout_ms, uint16_t monitor_timeout_ms, uint8_t num_tx_buffers, uint8_t num_rx_buffers, uint8_t * buffer, uint32_t size){
 
     log_info("L2CAP_ACCEPT_ERTM_CONNECTION local_cid 0x%x", local_cid);
     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
     if (!channel) {
         log_error("l2cap_accept_connection called but local_cid 0x%x not found", local_cid);
-        return;
+        return L2CAP_LOCAL_CID_DOES_NOT_EXIST;
     }
 
+    // validate local config
+    uint8_t result = l2cap_ertm_validate_local_config(max_transmit, retransmission_timeout_ms, monitor_timeout_ms, num_tx_buffers, num_rx_buffers, buffer, size);
+    if (result) return result;
+
     // configure L2CAP ERTM
     l2cap_ertm_configure_channel(channel, ertm_mandatory, max_transmit, retransmission_timeout_ms, monitor_timeout_ms, num_tx_buffers, num_rx_buffers, buffer, size);
 
@@ -1593,6 +1630,8 @@ void l2cap_accept_ertm_connection(uint16_t local_cid, int ertm_mandatory, uint8_
 
     // process
     l2cap_run();
+
+    return ERROR_CODE_SUCCESS;
 }
 #endif
 
diff --git a/src/l2cap.h b/src/l2cap.h
index 20688ff6a..8ea337028 100644
--- a/src/l2cap.h
+++ b/src/l2cap.h
@@ -364,8 +364,9 @@ void l2cap_accept_connection(uint16_t local_cid);
  * @param num_rx_buffers Number of packets that can be received out of order (-> our tx_window size)
  * @param buffer to store out-of-order packets and unacknowledged outgoing packets with their tretransmission timers
  * @param size of buffer
+ * @return status
  */
-void l2cap_accept_ertm_connection(uint16_t local_cid, int ertm_mandatory, uint8_t max_transmit,
+uint8_t l2cap_accept_ertm_connection(uint16_t local_cid, int ertm_mandatory, uint8_t max_transmit,
     uint16_t retransmission_timeout_ms, uint16_t monitor_timeout_ms, uint8_t num_tx_buffers, uint8_t num_rx_buffers, uint8_t * buffer, uint32_t size);
 
 /**