diff --git a/variable.variable.inc b/variable.variable.inc
index 0ab3331..815e2db 100644
--- a/variable.variable.inc
+++ b/variable.variable.inc
@@ -93,6 +93,7 @@ function variable_variable_type_info() {
     'element' => array('#type' => 'textfield', '#size' => 15, '#maxlength' => 10),
     'token' => TRUE,
     'validate callback' => 'variable_validate_number',
+    'format callback' => 'variable_format_string',
   );
   // Select multiple options from multiple choices
   $type['options'] = array(