diff --git a/ports/espressif/common-hal/wifi/Monitor.c b/ports/espressif/common-hal/wifi/Monitor.c
index f6d0e6e4d8f..8bb4eb98e23 100644
--- a/ports/espressif/common-hal/wifi/Monitor.c
+++ b/ports/espressif/common-hal/wifi/Monitor.c
@@ -30,6 +30,12 @@ static const char *TAG = "monitor";
 static void wifi_monitor_cb(void *recv_buf, wifi_promiscuous_pkt_type_t type) {
     wifi_promiscuous_pkt_t *pkt = (wifi_promiscuous_pkt_t *)recv_buf;
 
+    // Construct enables promiscuous mode before make_new sets the singleton.
+    wifi_monitor_obj_t *self = MP_STATE_VM(wifi_monitor_singleton);
+    if (self == NULL || common_hal_wifi_monitor_deinited(self)) {
+        return;
+    }
+
     // prepare packet
     monitor_packet_t packet = {
         .channel = pkt->rx_ctrl.channel,
@@ -43,14 +49,11 @@ static void wifi_monitor_cb(void *recv_buf, wifi_promiscuous_pkt_type_t type) {
         packet.payload = malloc(packet.length);
         if (packet.payload) {
             memcpy(packet.payload, pkt->payload, packet.length);
-            wifi_monitor_obj_t *self = MP_STATE_VM(wifi_monitor_singleton);
-            if (self->queue) {
-                // send packet
-                if (xQueueSendFromISR(self->queue, &packet, NULL) != pdTRUE) {
-                    self->lost++;
-                    free(packet.payload);
-                    ESP_LOGE(TAG, "packet queue full");
-                }
+            // send packet
+            if (xQueueSendFromISR(self->queue, &packet, NULL) != pdTRUE) {
+                self->lost++;
+                free(packet.payload);
+                ESP_LOGE(TAG, "packet queue full");
             }
         } else {
             ESP_LOGE(TAG, "not enough memory for packet");
@@ -97,13 +100,12 @@ void common_hal_wifi_monitor_construct(wifi_monitor_obj_t *self, uint8_t channel
     self->queue_length = queue;
 }
 
-bool common_hal_wifi_monitor_deinited(void) {
-    bool enabled;
-    return (esp_wifi_get_promiscuous(&enabled) == ESP_ERR_WIFI_NOT_INIT) ? true : !enabled;
+bool common_hal_wifi_monitor_deinited(wifi_monitor_obj_t *self) {
+    return self->queue == NULL;
 }
 
 void common_hal_wifi_monitor_deinit(wifi_monitor_obj_t *self) {
-    if (common_hal_wifi_monitor_deinited()) {
+    if (common_hal_wifi_monitor_deinited(self)) {
         return;
     }
 
@@ -119,6 +121,8 @@ void common_hal_wifi_monitor_deinit(wifi_monitor_obj_t *self) {
     }
     vQueueDelete(self->queue);
     self->queue = NULL;
+    // Root pointers outlive the VM heap.
+    MP_STATE_VM(wifi_monitor_singleton) = NULL;
 }
 
 void common_hal_wifi_monitor_set_channel(wifi_monitor_obj_t *self, uint8_t channel) {
diff --git a/ports/espressif/common-hal/wifi/__init__.c b/ports/espressif/common-hal/wifi/__init__.c
index 59172b17851..5895638e68c 100644
--- a/ports/espressif/common-hal/wifi/__init__.c
+++ b/ports/espressif/common-hal/wifi/__init__.c
@@ -576,7 +576,9 @@ void wifi_reset(void) {
     if (!wifi_inited) {
         return;
     }
-    common_hal_wifi_monitor_deinit(MP_STATE_VM(wifi_monitor_singleton));
+    if (MP_STATE_VM(wifi_monitor_singleton) != NULL) {
+        common_hal_wifi_monitor_deinit(MP_STATE_VM(wifi_monitor_singleton));
+    }
     wifi_radio_obj_t *radio = &common_hal_wifi_radio_obj;
     common_hal_wifi_radio_set_enabled(radio, false);
     #ifndef CONFIG_IDF_TARGET_ESP32
diff --git a/ports/raspberrypi/common-hal/wifi/Monitor.c b/ports/raspberrypi/common-hal/wifi/Monitor.c
index 8469c60ad56..58c49ab7916 100644
--- a/ports/raspberrypi/common-hal/wifi/Monitor.c
+++ b/ports/raspberrypi/common-hal/wifi/Monitor.c
@@ -23,7 +23,7 @@ void common_hal_wifi_monitor_construct(wifi_monitor_obj_t *self, uint8_t channel
     mp_raise_NotImplementedError(MP_ERROR_TEXT("wifi.Monitor not available"));
 }
 
-bool common_hal_wifi_monitor_deinited(void) {
+bool common_hal_wifi_monitor_deinited(wifi_monitor_obj_t *self) {
     return true;
 }
 
diff --git a/ports/zephyr-cp/common-hal/wifi/Monitor.c b/ports/zephyr-cp/common-hal/wifi/Monitor.c
index 7cacb8b520a..ca1f920a4c6 100644
--- a/ports/zephyr-cp/common-hal/wifi/Monitor.c
+++ b/ports/zephyr-cp/common-hal/wifi/Monitor.c
@@ -76,14 +76,14 @@ void common_hal_wifi_monitor_construct(wifi_monitor_obj_t *self, uint8_t channel
     // self->queue_length = queue;
 }
 
-bool common_hal_wifi_monitor_deinited(void) {
+bool common_hal_wifi_monitor_deinited(wifi_monitor_obj_t *self) {
     // bool enabled;
     // return (esp_wifi_get_promiscuous(&enabled) == ESP_ERR_WIFI_NOT_INIT) ? true : !enabled;
     return true;
 }
 
 void common_hal_wifi_monitor_deinit(wifi_monitor_obj_t *self) {
-    if (common_hal_wifi_monitor_deinited()) {
+    if (common_hal_wifi_monitor_deinited(self)) {
         return;
     }
 
diff --git a/shared-bindings/wifi/Monitor.c b/shared-bindings/wifi/Monitor.c
index 55a786c5428..fc321614d31 100644
--- a/shared-bindings/wifi/Monitor.c
+++ b/shared-bindings/wifi/Monitor.c
@@ -45,7 +45,7 @@ static mp_obj_t wifi_monitor_make_new(const mp_obj_type_t *type, size_t n_args,
     mp_int_t queue = mp_arg_validate_int_min(args[ARG_queue].u_int, 0, MP_QSTR_queue);
 
     wifi_monitor_obj_t *self = MP_STATE_VM(wifi_monitor_singleton);
-    if (common_hal_wifi_monitor_deinited()) {
+    if (self == NULL || common_hal_wifi_monitor_deinited(self)) {
         self = mp_obj_malloc_with_finaliser(wifi_monitor_obj_t, &wifi_monitor_type);
         common_hal_wifi_monitor_construct(self, channel, queue);
         MP_STATE_VM(wifi_monitor_singleton) = self;
@@ -109,7 +109,7 @@ MP_DEFINE_CONST_FUN_OBJ_1(wifi_monitor_lost_obj, wifi_monitor_obj_get_lost);
 //|         ...
 //|
 static mp_obj_t wifi_monitor_obj_get_queued(mp_obj_t self_in) {
-    if (common_hal_wifi_monitor_deinited()) {
+    if (common_hal_wifi_monitor_deinited(self_in)) {
         return mp_obj_new_int_from_uint(0);
     }
     return common_hal_wifi_monitor_get_queued(self_in);
@@ -122,7 +122,7 @@ MP_DEFINE_CONST_FUN_OBJ_1(wifi_monitor_queued_obj, wifi_monitor_obj_get_queued);
 //|
 //|
 static mp_obj_t wifi_monitor_obj_get_packet(mp_obj_t self_in) {
-    if (common_hal_wifi_monitor_deinited()) {
+    if (common_hal_wifi_monitor_deinited(self_in)) {
         raise_deinited_error();
     }
     return common_hal_wifi_monitor_get_packet(self_in);
diff --git a/shared-bindings/wifi/Monitor.h b/shared-bindings/wifi/Monitor.h
index c6a4ae6ecdf..cef14303522 100644
--- a/shared-bindings/wifi/Monitor.h
+++ b/shared-bindings/wifi/Monitor.h
@@ -13,7 +13,7 @@ extern const mp_obj_type_t wifi_monitor_type;
 void common_hal_wifi_monitor_construct(wifi_monitor_obj_t *self,
     uint8_t channel, size_t queue);
 void common_hal_wifi_monitor_deinit(wifi_monitor_obj_t *self);
-bool common_hal_wifi_monitor_deinited(void);
+bool common_hal_wifi_monitor_deinited(wifi_monitor_obj_t *self);
 
 void common_hal_wifi_monitor_set_channel(wifi_monitor_obj_t *self, uint8_t channel);
 mp_obj_t common_hal_wifi_monitor_get_channel(wifi_monitor_obj_t *self);