diff --git a/packages/bolt-connection/src/bolt/response-handler.js b/packages/bolt-connection/src/bolt/response-handler.js
index 4e540cfb4..6944c8ed4 100644
--- a/packages/bolt-connection/src/bolt/response-handler.js
+++ b/packages/bolt-connection/src/bolt/response-handler.js
@@ -76,7 +76,7 @@ export default class ResponseHandler {
     this._transformMetadata = transformMetadata || NO_OP_IDENTITY
     this._observer = Object.assign(
       {
-        onPendingObserversChange: NO_OP,
+        onObserversCountChange: NO_OP,
         onError: NO_OP,
         onFailure: NO_OP,
         onErrorApplyTransformation: NO_OP_IDENTITY
@@ -156,7 +156,11 @@ export default class ResponseHandler {
    */
   _updateCurrentObserver () {
     this._currentObserver = this._pendingObservers.shift()
-    this._observer.onPendingObserversChange(this._pendingObservers.length)
+    this._observer.onObserversCountChange(this._observersCount)
+  }
+
+  get _observersCount () {
+    return this._currentObserver == null ? this._pendingObservers.length : this._pendingObservers.length + 1
   }
 
   _queueObserver (observer) {
@@ -169,7 +173,7 @@ export default class ResponseHandler {
     } else {
       this._pendingObservers.push(observer)
     }
-    this._observer.onPendingObserversChange(this._pendingObservers.length)
+    this._observer.onObserversCountChange(this._observersCount)
     return true
   }
 
diff --git a/packages/bolt-connection/src/connection/connection-channel.js b/packages/bolt-connection/src/connection/connection-channel.js
index f291b7ec3..43f4fe121 100644
--- a/packages/bolt-connection/src/connection/connection-channel.js
+++ b/packages/bolt-connection/src/connection/connection-channel.js
@@ -67,7 +67,7 @@ export function createChannelConnection (
           server: conn.server,
           log: conn.logger,
           observer: {
-            onPendingObserversChange: conn._handleOngoingRequestsNumberChange.bind(conn),
+            onObserversCountChange: conn._handleOngoingRequestsNumberChange.bind(conn),
             onError: conn._handleFatalError.bind(conn),
             onFailure: conn._resetOnFailure.bind(conn),
             onProtocolError: conn._handleProtocolError.bind(conn),
diff --git a/packages/bolt-connection/test/bolt/response-handler.test.js b/packages/bolt-connection/test/bolt/response-handler.test.js
index e6d55cd42..3c75c1b98 100644
--- a/packages/bolt-connection/test/bolt/response-handler.test.js
+++ b/packages/bolt-connection/test/bolt/response-handler.test.js
@@ -22,6 +22,7 @@ const {
   logger: { Logger }
 } = internal
 
+const SUCCESS = 0x70 // 0111 0000 // SUCCESS <metadata>
 const FAILURE = 0x7f // 0111 1111 // FAILURE <metadata>
 
 describe('response-handler', () => {
@@ -69,4 +70,36 @@ describe('response-handler', () => {
       expect(receivedError.code).toBe(expectedError.code)
     })
   })
+
+  it('should keep track of observers and notify onObserversCountChange()', () => {
+    const observer = {
+      onObserversCountChange: jest.fn()
+    }
+    const responseHandler = new ResponseHandler({ observer, log: Logger.noOp() })
+
+    responseHandler._queueObserver({})
+    expect(observer.onObserversCountChange).toHaveBeenLastCalledWith(1)
+
+    responseHandler._queueObserver({})
+    expect(observer.onObserversCountChange).toHaveBeenLastCalledWith(2)
+
+    responseHandler._queueObserver({})
+    expect(observer.onObserversCountChange).toHaveBeenLastCalledWith(3)
+
+    const success = {
+      signature: SUCCESS,
+      fields: [{}]
+    }
+
+    responseHandler.handleResponse(success)
+    expect(observer.onObserversCountChange).toHaveBeenLastCalledWith(2)
+
+    responseHandler.handleResponse(success)
+    expect(observer.onObserversCountChange).toHaveBeenLastCalledWith(1)
+
+    responseHandler.handleResponse(success)
+    expect(observer.onObserversCountChange).toHaveBeenLastCalledWith(0)
+
+    expect(observer.onObserversCountChange).toHaveBeenCalledTimes(6)
+  })
 })
diff --git a/packages/neo4j-driver-deno/lib/bolt-connection/bolt/response-handler.js b/packages/neo4j-driver-deno/lib/bolt-connection/bolt/response-handler.js
index decc35b07..8a0aeddbf 100644
--- a/packages/neo4j-driver-deno/lib/bolt-connection/bolt/response-handler.js
+++ b/packages/neo4j-driver-deno/lib/bolt-connection/bolt/response-handler.js
@@ -76,7 +76,7 @@ export default class ResponseHandler {
     this._transformMetadata = transformMetadata || NO_OP_IDENTITY
     this._observer = Object.assign(
       {
-        onPendingObserversChange: NO_OP,
+        onObserversCountChange: NO_OP,
         onError: NO_OP,
         onFailure: NO_OP,
         onErrorApplyTransformation: NO_OP_IDENTITY
@@ -156,7 +156,11 @@ export default class ResponseHandler {
    */
   _updateCurrentObserver () {
     this._currentObserver = this._pendingObservers.shift()
-    this._observer.onPendingObserversChange(this._pendingObservers.length)
+    this._observer.onObserversCountChange(this._observersCount)
+  }
+
+  get _observersCount () {
+    return this._currentObserver == null ? this._pendingObservers.length : this._pendingObservers.length + 1
   }
 
   _queueObserver (observer) {
@@ -169,7 +173,7 @@ export default class ResponseHandler {
     } else {
       this._pendingObservers.push(observer)
     }
-    this._observer.onPendingObserversChange(this._pendingObservers.length)
+    this._observer.onObserversCountChange(this._observersCount)
     return true
   }
 
diff --git a/packages/neo4j-driver-deno/lib/bolt-connection/connection/connection-channel.js b/packages/neo4j-driver-deno/lib/bolt-connection/connection/connection-channel.js
index 6a4dbe193..eb6cc3777 100644
--- a/packages/neo4j-driver-deno/lib/bolt-connection/connection/connection-channel.js
+++ b/packages/neo4j-driver-deno/lib/bolt-connection/connection/connection-channel.js
@@ -67,7 +67,7 @@ export function createChannelConnection (
           server: conn.server,
           log: conn.logger,
           observer: {
-            onPendingObserversChange: conn._handleOngoingRequestsNumberChange.bind(conn),
+            onObserversCountChange: conn._handleOngoingRequestsNumberChange.bind(conn),
             onError: conn._handleFatalError.bind(conn),
             onFailure: conn._resetOnFailure.bind(conn),
             onProtocolError: conn._handleProtocolError.bind(conn),