diff --git a/image_captcha/image_captcha.module b/image_captcha/image_captcha.module
index 485510c..5ac4415 100644
--- a/image_captcha/image_captcha.module
+++ b/image_captcha/image_captcha.module
@@ -229,7 +229,13 @@ function image_captcha_captcha($op, $captcha_type='', $captcha_sid=NULL) {
         // Generate image source URL (add timestamp to avoid problems with
         // client side caching: subsequent images of the same CAPTCHA session
         // have the same URL, but should display a different code).
-        $img_src = check_url(url("image_captcha/$captcha_sid/" . REQUEST_TIME));
+        $options = array(
+          'query' => array(
+            'ts' => REQUEST_TIME,
+            'sid' => $captcha_sid,
+          ),
+        );
+        $img_src = check_url(url("image_captcha", $options));
         list($width, $height) = _image_captcha_image_size($code);
         // TODO: start using a theming funtion for generating the image markup?
         $result['form']['captcha_image'] = array(
diff --git a/image_captcha/image_captcha.user.inc b/image_captcha/image_captcha.user.inc
index 38434f4..2f7f964 100644
--- a/image_captcha/image_captcha.user.inc
+++ b/image_captcha/image_captcha.user.inc
@@ -11,12 +11,13 @@
 /**
  * Menu callback function that generates the CAPTCHA image.
  */
-function image_captcha_image($captcha_sid=NULL) {
+function image_captcha_image() {
   // If output buffering is on: discard current content and disable further buffering
   if (ob_get_level()) {
     ob_end_clean();
   }
   
+  $captcha_sid = $_GET['sid'];
   if (!$captcha_sid) {
     exit();
   }