diff --git a/core/lib/Drupal/Core/Routing/UrlGenerator.php b/core/lib/Drupal/Core/Routing/UrlGenerator.php
index 8e2522a..4eed246 100644
--- a/core/lib/Drupal/Core/Routing/UrlGenerator.php
+++ b/core/lib/Drupal/Core/Routing/UrlGenerator.php
@@ -134,6 +134,10 @@ protected function getInternalPathFromRoute(SymfonyRoute $route, $parameters = a
       unset($route_requirements['_scheme']);
     }
     $path = $this->doGenerate($compiledRoute->getVariables(), $route->getDefaults(), $route_requirements, $compiledRoute->getTokens(), $parameters, $route->getPath(), FALSE, $hostTokens);
+    if (strpos($path, '?') !== FALSE) {
+      list($path, $query) = explode('?', $path, 2);
+      $path .= '?' . strtr($query, $this->decodedChars);
+    }
 
     // The URL returned from doGenerate() will include the base path if there is
     // one (i.e., if running in a subdirectory) so we need to strip that off
diff --git a/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
index f5366f0..3530d3f 100644
--- a/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
+++ b/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
@@ -209,28 +209,56 @@ public function testAliasGenerationWithParameters() {
     $url = $this->generator->generate('test_2', array('narf' => '5'));
     $this->assertEquals('/goodbye/cruel/world', $url);
 
-    $this->routeProcessorManager->expects($this->exactly(3))
-      ->method('processOutbound')
-      ->with($this->anything());
-
-    $options = array('fragment' => 'top');
-    // Extra parameters should appear in the query string.
-    $url = $this->generator->generateFromRoute('test_1', array('zoo' => '5'), $options);
-    $this->assertEquals('/hello/world?zoo=5#top', $url);
-
-    $options = array('query' => array('page' => '1'), 'fragment' => 'bottom');
-    $url = $this->generator->generateFromRoute('test_2', array('narf' => '5'), $options);
-    $this->assertEquals('/goodbye/cruel/world?page=1#bottom', $url);
-
-    // Changing the parameters, the route still matches but there is no alias.
-    $url = $this->generator->generateFromRoute('test_2', array('narf' => '7'), $options);
-    $this->assertEquals('/test/two/7?page=1#bottom', $url);
-
     $path = $this->generator->getPathFromRoute('test_2', array('narf' => '5'));
     $this->assertEquals('test/two/5', $path);
   }
 
   /**
+   * Confirms that generated routes will have aliased paths with options.
+   *
+   * @dataProvider providerTestAliasGenerationWithOptions
+   */
+  public function testAliasGenerationWithOptions($route_name, $route_parameters, $options, $expected) {
+    $url = $this->generator->generateFromRoute($route_name, $route_parameters, $options);
+    $this->assertSame($expected, $url);
+  }
+
+  /**
+   * Provides test data for testAliasGenerationWithOptions.
+   */
+  public function providerTestAliasGenerationWithOptions() {
+    $data = [];
+    // Extra parameters should appear in the query string.
+    $data[] = [
+      'test_1',
+      ['zoo' => '5'],
+      ['fragment' => 'top'],
+      '/hello/world?zoo=5#top',
+    ];
+    $data[] = [
+      'test_2',
+      ['narf' => '5'],
+      ['query' => ['page' => '1'], 'fragment' => 'bottom'],
+      '/goodbye/cruel/world?page=1#bottom',
+    ];
+    // Changing the parameters, the route still matches but there is no alias.
+    $data[] = [
+      'test_2',
+      ['narf' => '7'],
+      ['query' => ['page' => '1'], 'fragment' => 'bottom'],
+      '/test/two/7?page=1#bottom',
+    ];
+    // Query string values containing '/' should be decoded.
+    $data[] = [
+      'test_2',
+      ['narf' => '7'],
+      ['query' => ['page' => '1/2'], 'fragment' => 'bottom'],
+      '/test/two/7?page=1/2#bottom',
+    ];
+    return $data;
+  }
+
+  /**
    * Tests URL generation from route with trailing start and end slashes.
    */
   public function testGetPathFromRouteTrailing() {