diff --git a/framework/caching/Cache.php b/framework/caching/Cache.php
index dd2ae4e4caf..6756fc6449c 100644
--- a/framework/caching/Cache.php
+++ b/framework/caching/Cache.php
@@ -135,7 +135,7 @@ public function get($key)
         if ($value === false || $this->serializer === false) {
             return $value;
         } elseif ($this->serializer === null) {
-            $value = unserialize($value);
+            $value = unserialize((string)$value);
         } else {
             $value = call_user_func($this->serializer[1], $value);
         }