diff --git a/core/modules/user/src/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php b/core/modules/user/src/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
index fec14c3262b13b3c77212dc2dfca8ca374a699b8..7eba82eec126e7b389936be8d5a8da783994d50c 100644
--- a/core/modules/user/src/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
+++ b/core/modules/user/src/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
@@ -10,8 +10,8 @@
 use Drupal\Core\Routing\RouteObjectInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
-use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
-use Symfony\Component\Routing\Exception\ResourceNotFoundException;
+use Symfony\Component\HttpKernel\Exception\HttpException;
+use Symfony\Component\Routing\Exception\ExceptionInterface;
 use Symfony\Component\Routing\Matcher\UrlMatcherInterface;
 
 /**
@@ -137,10 +137,7 @@ protected function isAdminPath(Request $request) {
           $path = $this->pathProcessorManager->processInbound(urldecode(rtrim($cloned_request->getPathInfo(), '/')), $cloned_request);
           $attributes = $this->router->match($path);
         }
-        catch (ResourceNotFoundException $e) {
-          return FALSE;
-        }
-        catch (AccessDeniedHttpException $e) {
+        catch (ExceptionInterface | HttpException) {
           return FALSE;
         }
         $route_object = $attributes[RouteObjectInterface::ROUTE_OBJECT];
diff --git a/core/modules/user/tests/modules/user_language_test/src/Controller/UserLanguageTestController.php b/core/modules/user/tests/modules/user_language_test/src/Controller/UserLanguageTestController.php
new file mode 100644
index 0000000000000000000000000000000000000000..280dafdaad8199b0e9dd72a2574f7a1222a1d04e
--- /dev/null
+++ b/core/modules/user/tests/modules/user_language_test/src/Controller/UserLanguageTestController.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace Drupal\user_language_test\Controller;
+
+/**
+ * Returns responses for User Language Test routes.
+ */
+class UserLanguageTestController {
+
+  /**
+   * Builds the response.
+   */
+  public function buildPostResponse() {
+    return ['#markup' => 'It works!'];
+  }
+
+}
diff --git a/core/modules/user/tests/modules/user_language_test/src/Form/UserLanguageTestForm.php b/core/modules/user/tests/modules/user_language_test/src/Form/UserLanguageTestForm.php
new file mode 100644
index 0000000000000000000000000000000000000000..f20d044840c2b4ce85e565f233a8a0ef080768ce
--- /dev/null
+++ b/core/modules/user/tests/modules/user_language_test/src/Form/UserLanguageTestForm.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace Drupal\user_language_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
+
+/**
+ * Provides a User Language Test form.
+ */
+class UserLanguageTestForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'user_language_test';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+
+    $form['#action'] = Url::fromRoute('user_language_test.post_response')->toString();
+
+    $form['actions'] = [
+      '#type' => 'actions',
+      'submit' => [
+        '#type' => 'submit',
+        '#value' => $this->t('Send'),
+      ],
+    ];
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+
+  }
+
+}
diff --git a/core/modules/user/tests/modules/user_language_test/user_language_test.info.yml b/core/modules/user/tests/modules/user_language_test/user_language_test.info.yml
new file mode 100644
index 0000000000000000000000000000000000000000..5df005c016de9de76075c89a096b7d553156cd73
--- /dev/null
+++ b/core/modules/user/tests/modules/user_language_test/user_language_test.info.yml
@@ -0,0 +1,5 @@
+name: 'User language tests'
+type: module
+description: 'Support module for user language testing.'
+package: Testing
+version: VERSION
diff --git a/core/modules/user/tests/modules/user_language_test/user_language_test.routing.yml b/core/modules/user/tests/modules/user_language_test/user_language_test.routing.yml
new file mode 100644
index 0000000000000000000000000000000000000000..c8ddc89d21f79c0c37d4f870ab96428b69c74caf
--- /dev/null
+++ b/core/modules/user/tests/modules/user_language_test/user_language_test.routing.yml
@@ -0,0 +1,16 @@
+user_language_test.post_response:
+  path: '/user-language-test/post'
+  defaults:
+    _controller: Drupal\user_language_test\Controller\UserLanguageTestController::buildPostResponse
+  methods: [post]
+  options:
+    _admin_route: TRUE
+  requirements:
+    _access: 'TRUE'
+
+user_language_test.form:
+  path: '/user-language-test/form'
+  defaults:
+    _form: 'Drupal\user_language_test\Form\UserLanguageTestForm'
+  requirements:
+    _access: 'TRUE'
diff --git a/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php b/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php
index 2b29e802e58156949d44ecd45ee424c6d1c688c8..1a19144c982790c035f078fc8a33233a008306e3 100644
--- a/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php
+++ b/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php
@@ -31,7 +31,7 @@ class UserAdminLanguageTest extends BrowserTestBase {
    *
    * @var array
    */
-  protected static $modules = ['user', 'language', 'language_test'];
+  protected static $modules = ['user', 'language', 'language_test', 'user_language_test'];
 
   /**
    * {@inheritdoc}
@@ -156,6 +156,13 @@ public function testActualNegotiation() {
     $this->drupalGet('xx/' . $path);
     $this->assertSession()->pageTextContains('Language negotiation method: language-user-admin');
 
+    // Make sure 'language-user-admin' plugin does not fail when a route is
+    // restricted to POST requests and language negotiation with the admin
+    // language method is used.
+    $this->drupalGet('/user-language-test/form');
+    $this->submitForm([], 'Send');
+    $this->assertSession()->statusCodeEquals(200);
+
     // Unset the preferred language code for the user.
     $edit = [];
     $edit['preferred_admin_langcode'] = '';