--- ./captcha.module.orig	2009-12-08 23:25:19.000000000 +0100
+++ ./captcha.module	2010-01-09 00:44:24.367138298 +0100
@@ -217,7 +217,7 @@
     // Generate a CAPTCHA and its solution
     // (note that the CAPTCHA session ID is given as third argument).
     $captcha = module_invoke($captcha_type_module, 'captcha', 'generate', $captcha_type_challenge, $captcha_sid);
-    if (!$captcha) {
+    if (empty($captcha)) {
       // The selected module returned nothing, maybe it is disabled or it's wrong, we should watchdog that and then quit.
       watchdog('CAPTCHA',
         'CAPTCHA problem: hook_captcha() of module %module returned nothing when trying to retrieve challenge type %type for form %form_id.',
@@ -241,17 +241,16 @@
     // Add pre_render callback for additional CAPTCHA processing.
     $element['#pre_render'] = array('captcha_pre_render_process');
 
+    // Store information for usage in the validation and pre_render phase.
+    $element['#captcha_info'] = array(
+      'form_id' => $this_form_id,
+      'module' => $captcha_type_module,
+      'type' => $captcha_type_challenge,
+      'captcha_sid' => $captcha_sid,
+      'solution' => $captcha['solution'],
+    );
   }
 
-  // Store information for usage in the validation and pre_render phase.
-  $element['#captcha_info'] = array(
-    'form_id' => $this_form_id,
-    'module' => $captcha_type_module,
-    'type' => $captcha_type_challenge,
-    'captcha_sid' => $captcha_sid,
-    'solution' => $captcha['solution'],
-  );
-
   return $element;
 }