diff --git a/mailpoet/lib/Migrator/Migrator.php b/mailpoet/lib/Migrator/Migrator.php
index 092bbea62b..02ca00a531 100644
--- a/mailpoet/lib/Migrator/Migrator.php
+++ b/mailpoet/lib/Migrator/Migrator.php
@@ -36,7 +36,7 @@ class Migrator {
     }
 
     foreach ($migrations as $migration) {
-      if ($migration['unknown'] || $migration['status'] === self::MIGRATION_STATUS_COMPLETED) {
+      if (!$migration['level'] || $migration['unknown'] || $migration['status'] === self::MIGRATION_STATUS_COMPLETED) {
         continue;
       }
 
diff --git a/mailpoet/lib/Migrator/Repository.php b/mailpoet/lib/Migrator/Repository.php
index 91d17920e2..30a56e01fe 100644
--- a/mailpoet/lib/Migrator/Repository.php
+++ b/mailpoet/lib/Migrator/Repository.php
@@ -50,7 +50,7 @@ class Repository {
   }
 
   /**
-   * Array of filenames.
+   * Array of migration filenames and types.
    * Db migrations are loaded first, then app migrations. This ensures that Db migrator is run before app migrations
    * @return array<array{level: string, name: string}>
    */
@@ -59,13 +59,17 @@ class Repository {
       $this->loadForLevel(self::MIGRATIONS_LEVEL_DB),
       $this->loadForLevel(self::MIGRATIONS_LEVEL_APP)
     );
-    $duplicateNames = array_diff_assoc(array_column($migrations, 'name'), array_unique(array_column($migrations, 'name')));
+    $migrationNames = array_column($migrations, 'name');
+    $duplicateNames = array_diff_assoc($migrationNames, array_unique($migrationNames));
     if (!empty($duplicateNames)) {
       throw MigratorException::duplicateMigrationNames($duplicateNames);
     }
     return $migrations;
   }
 
+  /**
+   * @return array<array{level: string, name: string}>
+   */
   private function loadForLevel(string $level): array {
     $files = new RecursiveIteratorIterator(
       new RecursiveDirectoryIterator($this->migrationsDir . '/' . $level, RecursiveDirectoryIterator::SKIP_DOTS)
diff --git a/mailpoet/lib/Migrator/Runner.php b/mailpoet/lib/Migrator/Runner.php
index 1d34e366f7..d34a10cb0f 100644
--- a/mailpoet/lib/Migrator/Runner.php
+++ b/mailpoet/lib/Migrator/Runner.php
@@ -25,7 +25,7 @@ class Runner {
     $this->namespace = $this->getMigrationsNamespace();
   }
 
-  public function runMigration(string $name, ?string $level): void {
+  public function runMigration(string $name, string $level): void {
     $className = $this->getClassName($name, $level);
 
     try {
@@ -40,7 +40,7 @@ class Runner {
     }
   }
 
-  private function getClassName(string $name, ?string $level): string {
+  private function getClassName(string $name, string $level): string {
     $className = $this->namespace . '\\' . $level . '\\' . $name;
     if (!class_exists($className)) {
       throw MigratorException::migrationClassNotFound($className);