diff --git a/source/MAC/IEEE802_15_4/mac_defines.h b/source/MAC/IEEE802_15_4/mac_defines.h
index 1a3e2e4cc119..8a1c2edc9d63 100644
--- a/source/MAC/IEEE802_15_4/mac_defines.h
+++ b/source/MAC/IEEE802_15_4/mac_defines.h
@@ -91,8 +91,12 @@ typedef enum arm_nwk_mlme_event_type {
     ARM_NWK_MAC_MLME_INDIRECT_DATA_POLL_AFTER_DATA = 5,
 } arm_nwk_mlme_event_type_e;
 
+#define ENHANCED_ACK_MAX_LENGTH 255
+
 typedef struct dev_driver_tx_buffer {
     uint8_t *buf;
+    uint8_t *enhanced_ack_buf;
+    uint16_t ack_len;
     uint16_t len;
     unsigned priority:2;
 } dev_driver_tx_buffer_s;
diff --git a/source/MAC/IEEE802_15_4/mac_mcps_sap.c b/source/MAC/IEEE802_15_4/mac_mcps_sap.c
index a2cebe4c26d2..f118770c330b 100644
--- a/source/MAC/IEEE802_15_4/mac_mcps_sap.c
+++ b/source/MAC/IEEE802_15_4/mac_mcps_sap.c
@@ -1688,7 +1688,15 @@ int8_t mcps_generic_ack_build(protocol_interface_rf_mac_setup_s *rf_ptr, const m
 
     //Add MHR length to total length
     frame_length += buffer->mac_header_length_with_security + buffer->security_mic_len;
-    if ((frame_length) > dev_driver->phy_MTU - 2) {
+    uint16_t ack_mtu_size;
+    if (ENHANCED_ACK_MAX_LENGTH > dev_driver->phy_MTU) {
+        ack_mtu_size = dev_driver->phy_MTU;
+    } else {
+        ack_mtu_size = ENHANCED_ACK_MAX_LENGTH;
+    }
+
+
+    if ((frame_length) > ack_mtu_size - 2) {
         buffer->status = MLME_FRAME_TOO_LONG;
 
         if (buffer->fcf_dsn.securityEnabled) {
@@ -1700,12 +1708,12 @@ int8_t mcps_generic_ack_build(protocol_interface_rf_mac_setup_s *rf_ptr, const m
     }
 
     rf_ptr->mac_tx_status.length = frame_length;
-    uint8_t *ptr = tx_buf->buf;
+    uint8_t *ptr = tx_buf->enhanced_ack_buf;
     if (dev_driver->phy_header_length) {
         ptr += dev_driver->phy_header_length;
     }
 
-    tx_buf->len = frame_length;
+    tx_buf->ack_len = frame_length;
     uint8_t *mhr_start = ptr;
     buffer->tx_time = mac_mcps_sap_get_phy_timestamp(rf_ptr) + 300; //Send 300 us later
 
@@ -1795,6 +1803,7 @@ static int8_t mcps_generic_packet_rebuild(protocol_interface_rf_mac_setup_s *rf_
 
 static int8_t mcps_pd_data_cca_trig(protocol_interface_rf_mac_setup_s *rf_ptr, mac_pre_build_frame_t *buffer)
 {
+    platform_enter_critical();
     mac_mlme_mac_radio_enable(rf_ptr);
     rf_ptr->macTxProcessActive = true;
     if (rf_ptr->rf_csma_extension_supported) {
@@ -1804,6 +1813,11 @@ static int8_t mcps_pd_data_cca_trig(protocol_interface_rf_mac_setup_s *rf_ptr, m
             cca_enabled = false;
             rf_ptr->mac_ack_tx_active = true;
         } else {
+            if (rf_ptr->mac_ack_tx_active) {
+                mac_csma_backoff_start(rf_ptr);
+                platform_exit_critical();
+                return -1;
+            }
             cca_enabled = true;
         }
         mac_pd_sap_set_phy_tx_time(rf_ptr, buffer->tx_time, cca_enabled);
@@ -1817,6 +1831,7 @@ static int8_t mcps_pd_data_cca_trig(protocol_interface_rf_mac_setup_s *rf_ptr, m
                 if (rf_ptr->active_pd_data_request) {
                     mac_csma_backoff_start(rf_ptr);
                 }
+                platform_exit_critical();
                 return -1;
             }
             mac_csma_backoff_start(rf_ptr);
@@ -1824,7 +1839,7 @@ static int8_t mcps_pd_data_cca_trig(protocol_interface_rf_mac_setup_s *rf_ptr, m
     } else {
         timer_mac_start(rf_ptr, MAC_TIMER_CCA, (uint16_t)(buffer->tx_time / 50));
     }
-
+    platform_exit_critical();
     return 0;
 }
 
diff --git a/source/MAC/IEEE802_15_4/mac_mlme.c b/source/MAC/IEEE802_15_4/mac_mlme.c
index 057e4fac1a62..51c63f329f09 100644
--- a/source/MAC/IEEE802_15_4/mac_mlme.c
+++ b/source/MAC/IEEE802_15_4/mac_mlme.c
@@ -983,6 +983,7 @@ void mac_mlme_data_base_deallocate(struct protocol_interface_rf_mac_setup *rf_ma
         eventOS_callback_timer_unregister(rf_mac->mac_mcps_timer);
 
         ns_dyn_mem_free(rf_mac->dev_driver_tx_buffer.buf);
+        ns_dyn_mem_free(rf_mac->dev_driver_tx_buffer.enhanced_ack_buf);
         ns_dyn_mem_free(rf_mac->mac_beacon_payload);
 
         mac_sec_mib_deinit(rf_mac);
diff --git a/source/MAC/IEEE802_15_4/mac_pd_sap.c b/source/MAC/IEEE802_15_4/mac_pd_sap.c
index 7903da01c524..8f71f73b3093 100644
--- a/source/MAC/IEEE802_15_4/mac_pd_sap.c
+++ b/source/MAC/IEEE802_15_4/mac_pd_sap.c
@@ -159,9 +159,19 @@ int8_t mac_plme_cca_req(protocol_interface_rf_mac_setup_s *rf_mac_setup) {
         return 0;
     }
 
-    if (dev_driver->tx(tx_buf->buf, tx_buf->len, 1, PHY_LAYER_PAYLOAD) == 0) {
+    uint8_t *buffer;
+    uint16_t length;
+    if (rf_mac_setup->mac_ack_tx_active) {
+        buffer = tx_buf->enhanced_ack_buf;
+        length = tx_buf->ack_len;
+    } else {
+        buffer = tx_buf->buf;
+        length = tx_buf->len;
+    }
+    if (dev_driver->tx(buffer, length, 1, PHY_LAYER_PAYLOAD) == 0) {
         return 0;
     }
+
     rf_mac_setup->macRfRadioTxActive = false;
     return -1;
 }
diff --git a/source/MAC/IEEE802_15_4/sw_mac.c b/source/MAC/IEEE802_15_4/sw_mac.c
index fc579a02d340..3c8dee0721c7 100644
--- a/source/MAC/IEEE802_15_4/sw_mac.c
+++ b/source/MAC/IEEE802_15_4/sw_mac.c
@@ -252,6 +252,22 @@ static int8_t ns_sw_mac_api_enable_mcps_ext(mac_api_t *api, mcps_data_indication
     cur->data_ind_ext_cb = data_ind_cb;
     cur->enhanced_ack_data_req_cb = ack_data_req_cb;
     if (data_cnf_cb && data_ind_cb && ack_data_req_cb) {
+        arm_device_driver_list_s *dev_driver = mac_store.setup->dev_driver;
+        ns_dyn_mem_free(mac_store.setup->dev_driver_tx_buffer.enhanced_ack_buf);
+
+        uint16_t total_length;
+        if (ENHANCED_ACK_MAX_LENGTH > dev_driver->phy_driver->phy_MTU) {
+            total_length = dev_driver->phy_driver->phy_MTU;
+        } else {
+            total_length = ENHANCED_ACK_MAX_LENGTH;
+        }
+
+        total_length += (dev_driver->phy_driver->phy_header_length + dev_driver->phy_driver->phy_tail_length);
+        mac_store.setup->dev_driver_tx_buffer.enhanced_ack_buf = ns_dyn_mem_alloc(total_length);
+        if (!mac_store.setup->dev_driver_tx_buffer.enhanced_ack_buf) {
+            return -2;
+        }
+
         mac_store.setup->mac_extension_enabled = true;
     } else {
         mac_store.setup->mac_extension_enabled = false;
diff --git a/test/nanostack/unittest/mac/mac_mcps_sap/Makefile b/test/nanostack/unittest/mac/mac_mcps_sap/Makefile
index ff2085bda092..9605389e2ede 100644
--- a/test/nanostack/unittest/mac/mac_mcps_sap/Makefile
+++ b/test/nanostack/unittest/mac/mac_mcps_sap/Makefile
@@ -26,6 +26,7 @@ TEST_SRC_FILES = \
         ../../stub/mac_pairwise_key_stub.c \
         ../../stub/protocol_stats_stub.c \
         ../../stub/ccm_security_stub.c \
+        ../../stub/platform_stub.c \
         ../../stub/fhss_config_stub.c \
 
 include ../../MakefileWorker.mk