diff --git a/phpstan.neon b/phpstan.neon
index e0291c80f3e79dd7177d2cae0968ec7cf9408794..6241b221674d1f0fabdda33517480b27c91e5ac3 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,5 +1,5 @@
 parameters:
-  level: 2
+  level: 3
   universalObjectCratesClasses:
     - Drupal\Core\Extension\Extension
   reportUnmatchedIgnoredErrors: true
@@ -24,6 +24,12 @@ parameters:
       paths:
         - tests/src/FunctionalJavascript
       reportUnmatched: false
+    # Caused by \Drupal\KernelTests\KernelTestBase::$container having the wrong type.
+    -
+      message: "#^Property Drupal\\\\KernelTests\\\\KernelTestBase\\:\\:\\$container \\(Drupal\\\\Core\\\\DependencyInjection\\\\ContainerBuilder\\) does not accept Drupal\\\\Component\\\\DependencyInjection\\\\ContainerInterface\\.$#"
+      paths:
+        - tests/src/Kernel/DatabaseTablesTest.php
+      reportUnmatched: false
 
     ### Package Manager
     # Caused by using self instead of static as a return type in \Drupal\fixture_manipulator\FixtureManipulator.
diff --git a/src/Controller/InstallerController.php b/src/Controller/InstallerController.php
index a06bfceabec9fba65aadf5939b5afcd6dae2a828..fd762a07ea24b2907245b74c8c0cc2e852464cd0 100644
--- a/src/Controller/InstallerController.php
+++ b/src/Controller/InstallerController.php
@@ -19,6 +19,7 @@ use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
 
 /**
  * Defines a controller to install projects via UI.
@@ -441,10 +442,10 @@ final class InstallerController extends ControllerBase {
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request.
    *
-   * @return \Symfony\Component\HttpFoundation\JsonResponse
+   * @return \Symfony\Component\HttpFoundation\Response
    *   Status message.
    */
-  public function activate(Request $request): JsonResponse {
+  public function activate(Request $request): Response {
     foreach ($request->toArray() as $project) {
       $project = $this->enabledSourceHandler->getStoredProject($project);
       $this->installState->setState($project, 'activating');