diff --git a/lib/weblib.php b/lib/weblib.php
index e079a47a5e1be..972ec7f392d7b 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -158,8 +158,11 @@ function strip_querystring($url) {
  * @return string
  */
 function get_referer() {
-
-    return strip_querystring(nvl($_SERVER['HTTP_REFERER']));
+    if (isset($_SERVER['HTTP_REFERER'])) {
+        return strip_querystring($_SERVER['HTTP_REFERER']);
+    } else {
+        return '';        
+    }
 }