Index: list.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/field/modules/list/list.module,v
retrieving revision 1.17
diff -u -r1.17 list.module
--- list.module	18 Oct 2009 18:46:11 -0000	1.17
+++ list.module	19 Oct 2009 21:17:17 -0000
@@ -161,11 +161,11 @@
   // field with the same name may have previously existed, as well
   // as when it is updated.
   $allowed_values = &drupal_static(__FUNCTION__, array());
-
+  
   if (isset($allowed_values[$field['field_name']])) {
     return $allowed_values[$field['field_name']];
   }
-
+  
   $allowed_values[$field['field_name']] = array();
 
   $function = $field['settings']['allowed_values_function'];
@@ -237,6 +237,10 @@
       form_error($element, t('The entered available values are not valid. All specified keys must be integers.'));
       break;
     }
+	elseif ($field_type == 'list_boolean' && ($key != '1' && $key != '0')) {
+      form_error($element, t('The entered available values are not valid. All specified keys must be 1 or 0.'));
+      break;
+    }
   }
 }