diff --git a/lib/util/sfToolkit.class.php b/lib/util/sfToolkit.class.php
index 543440ac0..03d17919a 100644
--- a/lib/util/sfToolkit.class.php
+++ b/lib/util/sfToolkit.class.php
@@ -254,7 +254,7 @@ public static function stringToArray($string)
       \s*(?:
         (?=\w+\s*=) | \s*$  # followed by another key= or the end of the string
       )
-    /x', $string, $matches, PREG_SET_ORDER);
+    /x', (string) $string, $matches, PREG_SET_ORDER);
 
         $attributes = array();
         foreach ($matches as $val) {
diff --git a/test/unit/util/sfToolkitTest.php b/test/unit/util/sfToolkitTest.php
index e40bfc308..6e9032131 100644
--- a/test/unit/util/sfToolkitTest.php
+++ b/test/unit/util/sfToolkitTest.php
@@ -10,7 +10,7 @@
 
 require_once __DIR__.'/../../bootstrap/unit.php';
 
-$t = new lime_test(95);
+$t = new lime_test(96);
 
 // ::stringToArray()
 $t->diag('::stringToArray()');
@@ -34,6 +34,8 @@
     $t->is(sfToolkit::stringToArray($string), $attributes, '->stringToArray()');
 }
 
+$t->is(sfToolkit::stringToArray(null), array(), '->stringToArray() can accept a null value');
+
 // ::isUTF8()
 $t->diag('::isUTF8()');
 $t->is(sfToolkit::isUTF8('été'), true, '::isUTF8() returns true if the parameter is an UTF-8 encoded string');