diff --git a/src/extensions/scratch3_ev3/index.js b/src/extensions/scratch3_ev3/index.js
index 667aaf5e8..ed47ffb5c 100644
--- a/src/extensions/scratch3_ev3/index.js
+++ b/src/extensions/scratch3_ev3/index.js
@@ -476,6 +476,7 @@ class EV3 {
         this._bt = null;
         this._runtime.registerPeripheralExtension(extensionId, this);
 
+        this.disconnect = this.disconnect.bind(this);
         this._onConnect = this._onConnect.bind(this);
         this._onMessage = this._onMessage.bind(this);
         this._pollValues = this._pollValues.bind(this);
@@ -561,7 +562,7 @@ class EV3 {
         this._bt = new BT(this._runtime, this._extensionId, {
             majorDeviceClass: 8,
             minorDeviceClass: 1
-        }, this._onConnect, this._onMessage);
+        }, this._onConnect, this.disconnect, this._onMessage);
     }
 
     /**
diff --git a/src/extensions/scratch3_microbit/index.js b/src/extensions/scratch3_microbit/index.js
index 3e880d8cd..b8fc23966 100644
--- a/src/extensions/scratch3_microbit/index.js
+++ b/src/extensions/scratch3_microbit/index.js
@@ -212,7 +212,7 @@ class MicroBit {
             filters: [
                 {services: [BLEUUID.service]}
             ]
-        }, this._onConnect);
+        }, this._onConnect, null);
     }
 
     /**
diff --git a/src/extensions/scratch3_wedo2/index.js b/src/extensions/scratch3_wedo2/index.js
index be285dee9..3edb87840 100644
--- a/src/extensions/scratch3_wedo2/index.js
+++ b/src/extensions/scratch3_wedo2/index.js
@@ -435,6 +435,7 @@ class WeDo2 {
          */
         this._batteryLevelIntervalId = null;
 
+        this.disconnect = this.disconnect.bind(this);
         this._onConnect = this._onConnect.bind(this);
         this._onMessage = this._onMessage.bind(this);
         this._checkBatteryLevel = this._checkBatteryLevel.bind(this);
@@ -593,7 +594,7 @@ class WeDo2 {
                 services: [BLEService.DEVICE_SERVICE]
             }],
             optionalServices: [BLEService.IO_SERVICE]
-        }, this._onConnect);
+        }, this._onConnect, this.disconnect);
     }
 
     /**
@@ -623,7 +624,6 @@ class WeDo2 {
         }
 
         if (this._batteryLevelIntervalId) {
-            console.log('clearing batterylevelintervalid');
             window.clearInterval(this._batteryLevelIntervalId);
             this._batteryLevelIntervalId = null;
         }
diff --git a/src/io/ble.js b/src/io/ble.js
index 1d9a208a9..afe384a7b 100644
--- a/src/io/ble.js
+++ b/src/io/ble.js
@@ -11,8 +11,9 @@ class BLE extends JSONRPCWebSocket {
      * @param {string} extensionId - the id of the extension using this socket.
      * @param {object} peripheralOptions - the list of options for peripheral discovery.
      * @param {object} connectCallback - a callback for connection.
+     * @param {object} disconnectCallback - a callback for disconnection.
      */
-    constructor (runtime, extensionId, peripheralOptions, connectCallback) {
+    constructor (runtime, extensionId, peripheralOptions, connectCallback, disconnectCallback = null) {
         const ws = new WebSocket(ScratchLinkWebSocket);
         super(ws);
 
@@ -25,9 +26,10 @@ class BLE extends JSONRPCWebSocket {
         this._connectCallback = connectCallback;
         this._connected = false;
         this._characteristicDidChangeCallback = null;
+        this._disconnectCallback = disconnectCallback;
+        this._discoverTimeoutID = null;
         this._extensionId = extensionId;
         this._peripheralOptions = peripheralOptions;
-        this._discoverTimeoutID = null;
         this._runtime = runtime;
     }
 
@@ -190,6 +192,9 @@ class BLE extends JSONRPCWebSocket {
         if (!this._connected) return;
 
         this._connected = false;
+        if (this._disconnectCallback) {
+            this._disconnectCallback();
+        }
 
         this._runtime.emit(this._runtime.constructor.PERIPHERAL_DISCONNECT_ERROR, {
             message: `Scratch lost connection to`,
diff --git a/src/io/bt.js b/src/io/bt.js
index 4c901bd87..bf393f76a 100644
--- a/src/io/bt.js
+++ b/src/io/bt.js
@@ -11,9 +11,10 @@ class BT extends JSONRPCWebSocket {
      * @param {string} extensionId - the id of the extension using this socket.
      * @param {object} peripheralOptions - the list of options for peripheral discovery.
      * @param {object} connectCallback - a callback for connection.
+     * @param {object} disconnectCallback - a callback for disconnection.
      * @param {object} messageCallback - a callback for message sending.
      */
-    constructor (runtime, extensionId, peripheralOptions, connectCallback, messageCallback) {
+    constructor (runtime, extensionId, peripheralOptions, connectCallback, disconnectCallback = null, messageCallback) {
         const ws = new WebSocket(ScratchLinkWebSocket);
         super(ws);
 
@@ -26,9 +27,10 @@ class BT extends JSONRPCWebSocket {
         this._connectCallback = connectCallback;
         this._connected = false;
         this._characteristicDidChangeCallback = null;
+        this._disconnectCallback = disconnectCallback;
+        this._discoverTimeoutID = null;
         this._extensionId = extensionId;
         this._peripheralOptions = peripheralOptions;
-        this._discoverTimeoutID = null;
         this._messageCallback = messageCallback;
         this._runtime = runtime;
     }
@@ -135,6 +137,9 @@ class BT extends JSONRPCWebSocket {
         if (!this._connected) return;
 
         this._connected = false;
+        if (this._disconnectCallback) {
+            this._disconnectCallback();
+        }
 
         this._runtime.emit(this._runtime.constructor.PERIPHERAL_DISCONNECT_ERROR, {
             message: `Scratch lost connection to`,