diff --git a/CHANGELOG.md b/CHANGELOG.md
index 68d69e6..57fd1f3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.6.3] - 2025-11-22
+
+### Fixed
+- Fixed **ArgumentNullException** when calling `Abort()` or accessing properties on completed requests ([#103](https://github.com/proyecto26/RestClient/issues/103)).
+- Enhanced disposal detection for UnityWebRequest objects to prevent crashes during cleanup scenarios.
+- Added proper exception handling for all RequestHelper properties that access disposed UnityWebRequest instances.
+- Improved thread safety for request cancellation in Unity's OnDestroy patterns.
+
 ## [2.6.2] - 2021-12-26
 
 ### Added
diff --git a/src/Proyecto26.RestClient/Helpers/RequestHelperExtension.cs b/src/Proyecto26.RestClient/Helpers/RequestHelperExtension.cs
index 7017a74..fadc6c3 100644
--- a/src/Proyecto26.RestClient/Helpers/RequestHelperExtension.cs
+++ b/src/Proyecto26.RestClient/Helpers/RequestHelperExtension.cs
@@ -20,7 +20,15 @@ public float UploadProgress
                 float progress = 0;
                 if (this.Request != null)
                 {
-                    progress = this.Request.uploadProgress;
+                    try
+                    {
+                        progress = this.Request.uploadProgress;
+                    }
+                    catch (ArgumentNullException)
+                    {
+                        // Request was disposed - return 0 progress
+                        progress = 0;
+                    }
                 }
                 return progress;
             }
@@ -36,7 +44,15 @@ public ulong UploadedBytes
                 ulong bytes = 0;
                 if (this.Request != null)
                 {
-                    bytes = this.Request.uploadedBytes;
+                    try
+                    {
+                        bytes = this.Request.uploadedBytes;
+                    }
+                    catch (ArgumentNullException)
+                    {
+                        // Request was disposed - return 0 bytes
+                        bytes = 0;
+                    }
                 }
                 return bytes;
             }
@@ -52,7 +68,15 @@ public float DownloadProgress
                 float progress = 0;
                 if (this.Request != null)
                 {
-                    progress = this.Request.downloadProgress;
+                    try
+                    {
+                        progress = this.Request.downloadProgress;
+                    }
+                    catch (ArgumentNullException)
+                    {
+                        // Request was disposed - return 0 progress
+                        progress = 0;
+                    }
                 }
                 return progress;
             }
@@ -68,7 +92,15 @@ public ulong DownloadedBytes
                 ulong bytes = 0;
                 if (this.Request != null)
                 {
-                    bytes = this.Request.downloadedBytes;
+                    try
+                    {
+                        bytes = this.Request.downloadedBytes;
+                    }
+                    catch (ArgumentNullException)
+                    {
+                        // Request was disposed - return 0 bytes
+                        bytes = 0;
+                    }
                 }
                 return bytes;
             }
@@ -81,10 +113,18 @@ public ulong DownloadedBytes
         /// <param name="name">The name of the header.</param>
         public string GetHeader(string name)
         {
-            string headerValue;
+            string headerValue = null;
             if (this.Request != null)
             {
-                headerValue = this.Request.GetRequestHeader(name);
+                try
+                {
+                    headerValue = this.Request.GetRequestHeader(name);
+                }
+                catch (ArgumentNullException)
+                {
+                    // Request was disposed - fall back to headers dictionary
+                    this.Headers.TryGetValue(name, out headerValue);
+                }
             }
             else
             {
@@ -131,6 +171,12 @@ public void Abort()
                         this.Request.Abort();
                     }
                 }
+                catch (ArgumentNullException)
+                {
+                    // Request was already disposed by UnityWebRequest's using block - this is expected behavior
+                    // No need to log this as it's a normal part of the request lifecycle
+                    HttpBase.DebugLog(this.EnableDebug, "Request was already disposed; abort skipped.", true);
+                }
                 catch (Exception error) {
                     HttpBase.DebugLog(this.EnableDebug, error.Message, true);
                 }
diff --git a/src/Proyecto26.RestClient/Proyecto26.RestClient.csproj b/src/Proyecto26.RestClient/Proyecto26.RestClient.csproj
index 9c255c1..edecf9f 100644
--- a/src/Proyecto26.RestClient/Proyecto26.RestClient.csproj
+++ b/src/Proyecto26.RestClient/Proyecto26.RestClient.csproj
@@ -9,7 +9,7 @@
     <AssemblyName>Proyecto26.RestClient</AssemblyName>
     <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
     <PackageId>Proyecto26.RestClient</PackageId>
-    <PackageVersion>2.6.2</PackageVersion>
+    <PackageVersion>2.6.3</PackageVersion>
     <Authors>jdnichollsc</Authors>
     <PackageIconUrl>https://github.com/proyecto26/RestClient/blob/master/img/icono.png?raw=true</PackageIconUrl>
     <PackageLicenseUrl>https://github.com/proyecto26/RestClient/blob/master/LICENSE</PackageLicenseUrl>
diff --git a/src/Proyecto26.RestClient/RestClient.cs b/src/Proyecto26.RestClient/RestClient.cs
index 82b0da5..2fbdd04 100644
--- a/src/Proyecto26.RestClient/RestClient.cs
+++ b/src/Proyecto26.RestClient/RestClient.cs
@@ -23,7 +23,7 @@ public static System.Version Version
             get
             {
                 if (_version == null) {
-                    _version = new System.Version("2.6.2");
+                    _version = new System.Version("2.6.3");
                 }
                 return _version;
             }
diff --git a/src/Proyecto26.RestClient/package.json b/src/Proyecto26.RestClient/package.json
index 29f6577..e71dc6f 100644
--- a/src/Proyecto26.RestClient/package.json
+++ b/src/Proyecto26.RestClient/package.json
@@ -1,6 +1,6 @@
 {
   "name": "com.proyecto26.restclient",
-  "version": "2.6.2",
+  "version": "2.6.3",
   "displayName": "RestClient for Unity",
   "description": "Simple HTTP and REST client for Unity based on Promises, also support Callbacks!",
   "unity": "2017.1",