diff --git a/mailpoet/lib/Automation/Engine/Control/ActionScheduler.php b/mailpoet/lib/Automation/Engine/Control/ActionScheduler.php
index 0834dc0c9b..1390acaa84 100644
--- a/mailpoet/lib/Automation/Engine/Control/ActionScheduler.php
+++ b/mailpoet/lib/Automation/Engine/Control/ActionScheduler.php
@@ -8,11 +8,13 @@ class ActionScheduler {
   private const GROUP_ID = 'mailpoet-automation';
 
   public function enqueue(string $hook, array $args = []): int {
-    return as_enqueue_async_action($hook, $args, self::GROUP_ID);
+    $result = as_enqueue_async_action($hook, $args, self::GROUP_ID);
+    return is_int($result) ? $result : 0;
   }
 
   public function schedule(int $timestamp, string $hook, array $args = []): int {
-    return as_schedule_single_action($timestamp, $hook, $args, self::GROUP_ID);
+    $result = as_schedule_single_action($timestamp, $hook, $args, self::GROUP_ID);
+    return is_int($result) ? $result : 0;
   }
 
   public function hasScheduledAction(string $hook, array $args = []): bool {
diff --git a/mailpoet/lib/Cron/ActionScheduler/ActionScheduler.php b/mailpoet/lib/Cron/ActionScheduler/ActionScheduler.php
index 73742135db..854db470f2 100644
--- a/mailpoet/lib/Cron/ActionScheduler/ActionScheduler.php
+++ b/mailpoet/lib/Cron/ActionScheduler/ActionScheduler.php
@@ -17,11 +17,13 @@ class ActionScheduler {
   }
 
   public function scheduleRecurringAction(int $timestamp, int $interval_in_seconds, string $hook, array $args = [], bool $unique = true): int {
-    return as_schedule_recurring_action($timestamp, $interval_in_seconds, $hook, $args, self::GROUP_ID, $unique);
+    $result = as_schedule_recurring_action($timestamp, $interval_in_seconds, $hook, $args, self::GROUP_ID, $unique);
+    return is_int($result) ? $result : 0;
   }
 
   public function scheduleImmediateSingleAction(string $hook, array $args = [], bool $unique = true): int {
-    return as_schedule_single_action($this->wp->currentTime('timestamp', true), $hook, $args, self::GROUP_ID, $unique);
+    $result = as_schedule_single_action($this->wp->currentTime('timestamp', true), $hook, $args, self::GROUP_ID, $unique);
+    return is_int($result) ? $result : 0;
   }
 
   public function unscheduleAction(string $hook, array $args = []): ?int {