diff --git a/devices/ble_hci/common-hal/_bleio/hci.c b/devices/ble_hci/common-hal/_bleio/hci.c
index ed9320330e..e261a98475 100644
--- a/devices/ble_hci/common-hal/_bleio/hci.c
+++ b/devices/ble_hci/common-hal/_bleio/hci.c
@@ -331,27 +331,27 @@ hci_result_t hci_poll_for_incoming_pkt(void) {
 
         switch (rx_buffer[0]) {
             case H4_ACL:
-                if (rx_idx > sizeof(h4_hci_acl_pkt_t)) {
+                if (rx_idx >= sizeof(h4_hci_acl_pkt_t)) {
                     const size_t total_len =
                         sizeof(h4_hci_acl_pkt_t) + ((h4_hci_acl_pkt_t *) rx_buffer)->data_len;
                     if (rx_idx == total_len) {
                         packet_is_complete = true;
                     }
                     if (rx_idx > total_len) {
-                        mp_printf(&mp_plat_print, "acl: rx_idx > total_len\n");
+                        return HCI_PACKET_SIZE_ERROR;
                     }
                 }
                 break;
 
             case H4_EVT:
-                if (rx_idx > sizeof(h4_hci_evt_pkt_t)) {
+                if (rx_idx >= sizeof(h4_hci_evt_pkt_t)) {
                     const size_t total_len =
                         sizeof(h4_hci_evt_pkt_t) + ((h4_hci_evt_pkt_t *) rx_buffer)->param_len;
                     if (rx_idx == total_len) {
                         packet_is_complete = true;
                     }
                     if (rx_idx > total_len) {
-                        mp_printf(&mp_plat_print, "evt: rx_idx > total_len\n");
+                        return HCI_PACKET_SIZE_ERROR;
                     }
                 }
                 break;
@@ -786,6 +786,10 @@ void hci_check_error(hci_result_t result) {
             mp_raise_bleio_BluetoothError(translate("Error writing to HCI adapter"));
             return;
 
+        case HCI_PACKET_SIZE_ERROR:
+            mp_raise_RuntimeError(translate("HCI packet size mismatch"));
+            return;
+
         case HCI_ATT_ERROR:
             mp_raise_RuntimeError(translate("Error in ATT protocol code"));
             return;
diff --git a/devices/ble_hci/common-hal/_bleio/hci.h b/devices/ble_hci/common-hal/_bleio/hci.h
index 3d082c49cb..c9fd2393af 100644
--- a/devices/ble_hci/common-hal/_bleio/hci.h
+++ b/devices/ble_hci/common-hal/_bleio/hci.h
@@ -29,14 +29,15 @@
 typedef struct _bleio_adapter_obj_t bleio_adapter_obj_t;
 
 // An hci_result_t is one of the HCI_x values below,
-// or is it > 0 and is an HCI command status value (see hci_include/hci_err.h)
+// or it is > 0 and is an HCI command status value (see hci_include/hci_err.h)
 typedef int hci_result_t;
-#define HCI_OK (0)
-#define HCI_RESPONSE_TIMEOUT (-1)
-#define HCI_WRITE_TIMEOUT (-2)
-#define HCI_READ_ERROR (-3)
-#define HCI_WRITE_ERROR (-4)
-#define HCI_ATT_ERROR (-5)
+#define HCI_OK                 (0)
+#define HCI_RESPONSE_TIMEOUT  (-1)
+#define HCI_WRITE_TIMEOUT     (-2)
+#define HCI_READ_ERROR        (-3)
+#define HCI_WRITE_ERROR       (-4)
+#define HCI_ATT_ERROR         (-5)
+#define HCI_PACKET_SIZE_ERROR (-6)
 
 extern void bleio_hci_reset(void);