diff --git a/Container.php b/Container.php
index 9d16f9c27..740150bf2 100644
--- a/Container.php
+++ b/Container.php
@@ -320,11 +320,11 @@ public function reset()
     /**
      * Gets all service ids.
      *
-     * @return array An array of all defined service ids
+     * @return string[] An array of all defined service ids
      */
     public function getServiceIds()
     {
-        return array_unique(array_merge(['service_container'], array_keys($this->fileMap), array_keys($this->methodMap), array_keys($this->services)));
+        return array_map('strval', array_unique(array_merge(['service_container'], array_keys($this->fileMap), array_keys($this->methodMap), array_keys($this->services))));
     }
 
     /**
diff --git a/ContainerBuilder.php b/ContainerBuilder.php
index 497064cdd..d9227be24 100644
--- a/ContainerBuilder.php
+++ b/ContainerBuilder.php
@@ -775,13 +775,11 @@ public function compile(bool $resolveEnvPlaceholders = false)
     }
 
     /**
-     * Gets all service ids.
-     *
-     * @return array An array of all defined service ids
+     * {@inheritdoc}
      */
     public function getServiceIds()
     {
-        return array_unique(array_merge(array_keys($this->getDefinitions()), array_keys($this->aliasDefinitions), parent::getServiceIds()));
+        return array_map('strval', array_unique(array_merge(array_keys($this->getDefinitions()), array_keys($this->aliasDefinitions), parent::getServiceIds())));
     }
 
     /**