diff --git a/public/modules/custom/helfi_kymp_content/helfi_kymp_content.module b/public/modules/custom/helfi_kymp_content/helfi_kymp_content.module
index 738395315..1578dfef2 100644
--- a/public/modules/custom/helfi_kymp_content/helfi_kymp_content.module
+++ b/public/modules/custom/helfi_kymp_content/helfi_kymp_content.module
@@ -5,6 +5,8 @@
  * Contains alterations for content.
  */
 
+declare(strict_types=1);
+
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Entity\ContentEntityInterface;
 use Drupal\Core\Entity\EntityFormInterface;
diff --git a/public/modules/custom/helfi_kymp_content/src/EventSubscriber/SearchApiSubscriber.php b/public/modules/custom/helfi_kymp_content/src/EventSubscriber/SearchApiSubscriber.php
index 0ad9d19a5..8393e069e 100644
--- a/public/modules/custom/helfi_kymp_content/src/EventSubscriber/SearchApiSubscriber.php
+++ b/public/modules/custom/helfi_kymp_content/src/EventSubscriber/SearchApiSubscriber.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\helfi_kymp_content\EventSubscriber;
 
 use Drupal\search_api\Event\ReindexScheduledEvent;
diff --git a/public/modules/custom/helfi_kymp_content/src/Plugin/DataType/StreetData.php b/public/modules/custom/helfi_kymp_content/src/Plugin/DataType/StreetData.php
index 3e206f8b9..7c7163c23 100644
--- a/public/modules/custom/helfi_kymp_content/src/Plugin/DataType/StreetData.php
+++ b/public/modules/custom/helfi_kymp_content/src/Plugin/DataType/StreetData.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\helfi_kymp_content\Plugin\DataType;
 
 use Drupal\Core\TypedData\DataDefinition;
diff --git a/public/modules/custom/helfi_kymp_content/src/Plugin/search_api/datasource/HelfiStreetDataSource.php b/public/modules/custom/helfi_kymp_content/src/Plugin/search_api/datasource/HelfiStreetDataSource.php
index 8d13c4a76..9663086fb 100644
--- a/public/modules/custom/helfi_kymp_content/src/Plugin/search_api/datasource/HelfiStreetDataSource.php
+++ b/public/modules/custom/helfi_kymp_content/src/Plugin/search_api/datasource/HelfiStreetDataSource.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\helfi_kymp_content\Plugin\search_api\datasource;
 
 use Drupal\Core\Language\LanguageInterface;
diff --git a/public/modules/custom/helfi_kymp_content/src/TypedData/StreetDataDefinition.php b/public/modules/custom/helfi_kymp_content/src/TypedData/StreetDataDefinition.php
index cfcd894ab..61a4cc2fa 100644
--- a/public/modules/custom/helfi_kymp_content/src/TypedData/StreetDataDefinition.php
+++ b/public/modules/custom/helfi_kymp_content/src/TypedData/StreetDataDefinition.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\helfi_kymp_content\TypedData;
 
 use Drupal\Core\TypedData\ComplexDataDefinitionBase;
diff --git a/public/modules/custom/helfi_kymp_migrations/src/TaxonomyMigrationService.php b/public/modules/custom/helfi_kymp_migrations/src/TaxonomyMigrationService.php
index b37661f4c..90ec9b809 100644
--- a/public/modules/custom/helfi_kymp_migrations/src/TaxonomyMigrationService.php
+++ b/public/modules/custom/helfi_kymp_migrations/src/TaxonomyMigrationService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\helfi_kymp_migrations;
 
 use Drupal\Core\Entity\EntityTypeManagerInterface;
diff --git a/public/modules/custom/helfi_kymp_plans/helfi_kymp_plans.module b/public/modules/custom/helfi_kymp_plans/helfi_kymp_plans.module
index db53b778a..3e2d7d389 100644
--- a/public/modules/custom/helfi_kymp_plans/helfi_kymp_plans.module
+++ b/public/modules/custom/helfi_kymp_plans/helfi_kymp_plans.module
@@ -5,6 +5,8 @@
  * Contains KYMP plans related functionalities.
  */
 
+declare(strict_types=1);
+
 /**
  * Implements hook_theme().
  */