Index: includes/image.gd.inc
===================================================================
--- includes/image.gd.inc	(revision 1)
+++ includes/image.gd.inc	(working copy)
@@ -23,7 +23,6 @@
  */
 function image_gd_settings() {
   if (image_gd_check_settings()) {
-    $form = array();
     $form['status'] = array(
       '#value' => t('The GD toolkit is installed and working properly.')
     );
@@ -38,15 +37,23 @@
       '#field_suffix' => t('%'),
     );
     $form['#element_validate'] = array('image_gd_settings_validate');
-    
+
     return $form;
   }
   else {
-    form_set_error('image_toolkit', t('The GD image toolkit requires that the GD module for PHP be installed and configured properly. For more information see <a href="@url">PHP\'s image documentation</a>.', array('@url' => 'http://php.net/image')));
-    return FALSE;
+    $form['#after_build'] = array('_image_gd_settings_missing');
   }
+  return $form;
 }
 
+function _image_gd_settings_missing($form, $form_state) {
+  // Don't report errors if another toolkit is being selected.
+  if (!isset($form['#post']['image_toolkit']) || $form['#post']['image_toolkit'] == 'gd') {
+    form_set_error('image_toolkit', t('The built-in GD image toolkit requires that the GD module for PHP be installed and configured properly. For more information see <a href="@url">PHP\'s image documentation</a>.', array('@url' => 'http://php.net/image')));
+  }
+  return $form;
+}
+
 /**
  * Validate the submitted GD settings.
  */