diff --git a/OLE/ChainedBlockStream.php b/OLE/ChainedBlockStream.php
index 49bfcbb..88255b1 100644
--- a/OLE/ChainedBlockStream.php
+++ b/OLE/ChainedBlockStream.php
@@ -144,7 +144,9 @@ function stream_open($path, $mode, $options, &$openedPath)
     function stream_close()
     {
         $this->ole = null;
-        unset($GLOBALS['_OLE_INSTANCES']);
+        if (isset($GLOBALS)) {
+            unset($GLOBALS['_OLE_INSTANCES']);
+        }
     }
 
     /**