diff --git a/core/includes/common.inc b/core/includes/common.inc
index 9601c76..52c5bfa 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3425,7 +3425,8 @@ function drupal_clear_css_cache() {
  */
 function drupal_delete_file_if_stale($uri) {
   // Default stale file threshold is 30 days.
-  if (REQUEST_TIME - filemtime($uri) > variable_get('drupal_stale_file_threshold', 2592000)) {
+  $threshold = state()->get('system.stale_file_threshold') ?: 2592000;
+  if (REQUEST_TIME - filemtime($uri) > $threshold) {
     file_unmanaged_delete($uri);
   }
 }
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index e938128..34a598f 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -2215,6 +2215,25 @@ function system_update_8032() {
 }
 
 /**
+ * Converts common.inc variables to the state system.
+ *
+ * @ingroup state_upgrade
+ */
+function system_update_7033() {
+  // Old variable names as keys, new state names as values.
+  $variables = array(
+    'drupal_stale_file_threshold' => 'system.stale_file_threshold',
+  );
+  // Convert any saved variables to the state system.
+  foreach ($variables as $variable_name => $state_name) {
+    if ($value = update_variable_get($variable_name, FALSE)) {
+      state()->set($state_name, $value);
+    }
+    update_variable_del($variable_name);
+  }
+}
+
+/**
  * @} End of "defgroup updates-7.x-to-8.x".
  * The next series of updates should start at 9000.
  */