diff --git a/CHANGELOG.md b/CHANGELOG.md
index d4b04a44..17475dce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## [2.4.0]
+
+- Add custom properties to a KuzzleRequest
+
 ## [2.3.0]
 
 - Add an option to accept bad SSL certificate
diff --git a/doc/2/core-classes/kuzzle/query/index.md b/doc/2/core-classes/kuzzle/query/index.md
index 9948e1ab..5b5f41c7 100644
--- a/doc/2/core-classes/kuzzle/query/index.md
+++ b/doc/2/core-classes/kuzzle/query/index.md
@@ -24,7 +24,7 @@ This is a low-level method, exposed to allow advanced SDK users to bypass high-l
 
 | Argument  | Type              | Description            |
 | --------- | ----------------- | ---------------------- |
-| `request` | <pre>KuzzleRequest</pre> | API request    |
+| `request` | <pre>[KuzzleRequest](/sdk/dart/2/core-classes/request)</pre> | API request    |
 | `volatile`   | <pre>Map<String, dynamic></pre> | Additional information to send to Kuzzle |
 | `queueable`   | <pre>bool</pre> | If true, queues the request during downtime, until connected to Kuzzle again |
 
diff --git a/doc/2/core-classes/request/index.md b/doc/2/core-classes/request/index.md
new file mode 100644
index 00000000..5606888f
--- /dev/null
+++ b/doc/2/core-classes/request/index.md
@@ -0,0 +1,7 @@
+---
+code: true
+type: branch
+title: KuzzleRequest
+description: KuzzleRequest object documentation
+order: 0
+---
\ No newline at end of file
diff --git a/doc/2/core-classes/request/introduction/index.md b/doc/2/core-classes/request/introduction/index.md
new file mode 100644
index 00000000..be91aa39
--- /dev/null
+++ b/doc/2/core-classes/request/introduction/index.md
@@ -0,0 +1,36 @@
+---
+code: false
+type: page
+title: Introduction
+description: KuzzleRequest object description
+order: 0
+---
+
+## KuzzleRequest
+
+`KuzzleRequest` is a **serializable** class representing a raw Kuzzle request.
+
+
+## Properties
+
+| Property | Type | Description |
+|--- |--- |--- |
+| `action` | <pre>String</pre> | Executed Kuzzle API controller's action `
+| `body` | <pre>Map<String, dynamic> body</pre> |
+| `collection` | <pre>String</pre> | Impacted collection |
+| `controller` | <pre>String</pre> | Executed Kuzzle API controller |
+| `index` | <pre>String</pre> | Impacted index |
+| `jwt` | <pre>String</pre> | Authentication token |
+| `lang` | <pre>String</pre> | ES lang |
+| `requestId` | <pre>String</pre> | Request unique identifier |
+| `waitForRefresh` | <pre>bool</pre> | If set to `true`, Kuzzle will wait for the persistence layer to finish indexing |
+| `volatile` | <pre>Map<String, dynamic></pre> | Volatile data |
+| `from`     | <pre>int</pre><br/>(`0`)    | Offset of the first document to fetch |
+| `size`     | <pre>int</pre><br/>(`10`)   | Maximum number of documents to retrieve per page |
+| `scroll`   | <pre>String</pre><br/>(`""`)    | When set, gets a forward-only cursor having its ttl set to the given value (ie `1s`; cf [elasticsearch time limits](https://www.elastic.co/guide/en/elasticsearch/reference/7.3/common-options.html#time-units)) |
+| `scrollId` | <pre>String</pre> | The scrollId if using scroll option |
+| `sort` | <pre>List<dynamic></pre> | Contains a list of fields, used to [sort search results](https://www.elastic.co/guide/en/elasticsearch/reference/7.3/search-request-sort.html), in order of importance. |
+
+## Overrided operators
+
+The `[]` and `[]=` are overrided so you can dynamically add any args you want to this class and it will be taken in consideration in the request sent to Kuzzle.
diff --git a/lib/src/kuzzle/request.dart b/lib/src/kuzzle/request.dart
index c4fc9abe..a4ff77ab 100644
--- a/lib/src/kuzzle/request.dart
+++ b/lib/src/kuzzle/request.dart
@@ -111,8 +111,13 @@ class KuzzleRequest {
     includeKuzzleMeta = data['includeKuzzleMeta'] as bool;
   }
 
+  final Map<String, dynamic> _args = {};
+
+  dynamic operator [](String key) => _args[key];
+  void operator []=(String key, dynamic value) => _args[key] = value;
+
   Map toJson() {
-    final map = <String, dynamic>{};
+    final map = _args;
 
     if (action != null) {
       map['action'] = action;
diff --git a/lib/src/protocols/abstract.dart b/lib/src/protocols/abstract.dart
index af871e90..e82df6e7 100644
--- a/lib/src/protocols/abstract.dart
+++ b/lib/src/protocols/abstract.dart
@@ -123,6 +123,15 @@ abstract class KuzzleProtocol extends KuzzleEventEmitter {
       final syncRes = send(request);
       // If we use a synchronous protocol the result is returned directly
       if (syncRes != null) {
+        syncRes.then((response) {
+          if (response.error != null) {
+            emit(ProtocolEvents.QUERY_ERROR, [response, request]);
+          }
+        }).catchError((err) {
+          emit(ProtocolEvents.QUERY_ERROR, [{
+            'error': err,
+          }, request]);
+        });
         return syncRes;
       }
     } on Exception catch (error) {
diff --git a/pubspec.yaml b/pubspec.yaml
index 003d0f04..0d9830d3 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: kuzzle
-version: 2.3.0
+version: 2.4.0
 description: A library to interact with kuzzle API. A backend software,
   self-hostable and ready to use to power modern cross-platform apps.
 homepage: https://github.com/kuzzleio/sdk-dart