diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index becda60..50d0923 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,4 +38,8 @@ jobs:
       - name: Run PHPCS
         run: |
           cd $DRUPAL_ROOT
-          vendor/bin/phpcs public/themes/contrib/$THEME_NAME --extensions=php,theme,module --standard=Drupal
+          vendor/bin/phpcs public/themes/contrib/$THEME_NAME --extensions=php,theme,module --standard=Drupal,DrupalPractice
+
+      - name: Run phpstan
+        working-directory: ${{ env.DRUPAL_ROOT }}
+        run: vendor/bin/phpstan analyze -c public/themes/contrib/$THEME_NAME/phpstan.neon public/themes/contrib/$THEME_NAME
diff --git a/hdbt_admin.theme b/hdbt_admin.theme
index 5aa4362..c6753be 100644
--- a/hdbt_admin.theme
+++ b/hdbt_admin.theme
@@ -5,6 +5,7 @@
  * Contains HDBT Admin theme.
  */
 
+use Drupal\Core\Entity\EntityFormInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\media\MediaInterface;
@@ -118,8 +119,11 @@ function hdbt_admin_form_node_form_alter(&$form, FormStateInterface $form_state,
   hdbt_admin_apply_form_theme($form);
 
   // Get current entity.
+  $formObject = $form_state->getFormObject();
+  assert($formObject instanceof EntityFormInterface);
+
   /** @var \Drupal\node\NodeInterface $node */
-  $node = $form_state->getFormObject()->getEntity();
+  $node = $formObject->getEntity();
 
   // Disable "Preview" button on new nodes.
   if ($node->isNew()) {
@@ -396,6 +400,7 @@ function hdbt_admin_preprocess_media(&$variables) {
     }
 
     if ($variables['media']->hasTranslation($current_language)) {
+      // @phpstan-ignore-next-line
       $alt = $variables['media']
         ->getTranslation($current_language)->field_media_image->alt;
       $variables['alt_text'] = $alt !== '""' ? $alt : FALSE;
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 0000000..582bde0
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,13 @@
+parameters:
+  fileExtensions:
+      - php
+      - module
+      - install
+      - theme
+  paths:
+    - ./
+  excludePaths:
+    - vendor
+  level: 3
+  checkMissingIterableValueType: false
+  treatPhpDocTypesAsCertain: false