diff --git a/Action/PurchaseAction.php b/Action/PurchaseAction.php
index 1601f9f..b0fae7a 100644
--- a/Action/PurchaseAction.php
+++ b/Action/PurchaseAction.php
@@ -78,7 +78,9 @@ public function execute($request)
 
             if ($details['CANCELURL']) {
                 $cancelUrl = Url::createFromUrl($details['CANCELURL']);
-                $cancelUrl->setQuery(['cancelled' => 1]);
+                $query = $cancelUrl->getQuery();
+                $query->modify(['cancelled' => 1]);
+                $cancelUrl->setQuery($query);
 
                 $details['CANCELURL'] = (string) $cancelUrl;
             }
diff --git a/Tests/Action/AutorizeActionTest.php b/Tests/Action/AutorizeActionTest.php
index ebfc89e..48b8e8e 100644
--- a/Tests/Action/AutorizeActionTest.php
+++ b/Tests/Action/AutorizeActionTest.php
@@ -262,6 +262,42 @@ public function shouldSetTokenTargetUrlAsCancelUrlIfCapturePassedWithToken()
         $action->execute($request);
     }
 
+    /**
+     * @test
+     */
+    public function shouldNotLooseExistingGetParamWhenSettingTargetUrlAsCancelUrl()
+    {
+        $testCase = $this;
+
+        $cancelUrl = 'http://theCancelUrl/?existingGetParam=testValue';
+        $expectedCancelUrl = $cancelUrl.'&cancelled=1';
+
+        $token = new Token();
+        $token->setTargetUrl($cancelUrl);
+        $token->setDetails(array());
+
+        $gatewayMock = $this->createGatewayMock();
+
+        $gatewayMock
+            ->expects($this->at(1))
+            ->method('execute')
+            ->with($this->isInstanceOf(SetExpressCheckout::class))
+            ->will($this->returnCallback(function ($request) use ($testCase, $expectedCancelUrl) {
+                $model = $request->getModel();
+
+                $testCase->assertEquals($expectedCancelUrl, $model['CANCELURL']);
+            }))
+        ;
+
+        $action = new AuthorizeAction();
+        $action->setGateway($gatewayMock);
+
+        $request = new Authorize($token);
+        $request->setModel(array());
+
+        $action->execute($request);
+    }
+
     /**
      * @test
      */
diff --git a/Tests/Action/CaptureActionTest.php b/Tests/Action/CaptureActionTest.php
index fe98959..639776b 100644
--- a/Tests/Action/CaptureActionTest.php
+++ b/Tests/Action/CaptureActionTest.php
@@ -261,6 +261,42 @@ public function shouldSetTokenTargetUrlAsCancelUrlIfCapturePassedWithToken()
         $action->execute($request);
     }
 
+    /**
+     * @test
+     */
+    public function shouldNotLooseExistingGetParamWhenSettingTargetUrlAsCancelUrl()
+    {
+        $testCase = $this;
+
+        $cancelUrl = 'http://theCancelUrl/?existingGetParam=testValue';
+        $expectedCancelUrl = $cancelUrl.'&cancelled=1';
+
+        $token = new Token();
+        $token->setTargetUrl($cancelUrl);
+        $token->setDetails(array());
+
+        $gatewayMock = $this->createGatewayMock();
+
+        $gatewayMock
+            ->expects($this->at(1))
+            ->method('execute')
+            ->with($this->isInstanceOf(SetExpressCheckout::class))
+            ->will($this->returnCallback(function ($request) use ($testCase, $expectedCancelUrl) {
+                $model = $request->getModel();
+
+                $testCase->assertEquals($expectedCancelUrl, $model['CANCELURL']);
+            }))
+        ;
+
+        $action = new CaptureAction();
+        $action->setGateway($gatewayMock);
+
+        $request = new Capture($token);
+        $request->setModel(array());
+
+        $action->execute($request);
+    }
+
     /**
      * @test
      */