diff --git a/cache/locks/file/lib.php b/cache/locks/file/lib.php
index b726cb7ee83..6094c53a38f 100644
--- a/cache/locks/file/lib.php
+++ b/cache/locks/file/lib.php
@@ -203,7 +203,7 @@ class cachelock_file implements cache_lock_interface {
      * @param string $ownerid
      */
     public function check_state($key, $ownerid) {
-        if (key_exists($key, $this->locks)) {
+        if (array_key_exists($key, $this->locks)) {
             // The key is locked and we own it.
             return true;
         }
@@ -234,4 +234,4 @@ class cachelock_file implements cache_lock_interface {
             @unlink($lockfile);
         }
     }
-}
\ No newline at end of file
+}