diff --git a/core/includes/schema.inc b/core/includes/schema.inc
index 0242006..e4e2a29 100644
--- a/core/includes/schema.inc
+++ b/core/includes/schema.inc
@@ -106,7 +106,7 @@ function drupal_set_installed_schema_version($module, $version) {
   \Drupal::keyValue('system.schema')->set($module, $version);
   // Store the information in config so that we can ensure that database updates
   // are the same between the source and the target site instances.
-  \Drupal::configFactory()->getEditable('core.extension')->set("versions.$module.schema", $version);
+  \Drupal::configFactory()->getEditable('core.extension')->set("versions.$module.schema", (string) $version);
   // Reset the static cache of module schema versions.
   drupal_get_installed_schema_version(NULL, TRUE);
 }
diff --git a/core/lib/Drupal/Core/Extension/ModuleInstaller.php b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
index 9df8b9e..afd9bd2 100644
--- a/core/lib/Drupal/Core/Extension/ModuleInstaller.php
+++ b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
@@ -304,7 +304,7 @@ public function install(array $module_list, $enable_dependencies = TRUE) {
         $versions[$module_name] = [
           'current' => $info['version'],
           'install' => $info['version'],
-          'schema' => drupal_get_installed_schema_version($module_name),
+          'schema' => (string) drupal_get_installed_schema_version($module_name),
         ];
       }
       ksort($versions);
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index a8c07c1..1bb80d1 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -1884,7 +1884,7 @@ function system_update_8015() {
     $versions[$module] = [
       'current' => $version,
       'install' => $version,
-      'schema' => drupal_get_installed_schema_version($module),
+      'schema' => (string) drupal_get_installed_schema_version($module),
     ];
   }
   foreach (\Drupal::service('theme_handler')->listInfo() as $theme => $extension) {