Index: og_user_roles.module
===================================================================
--- og_user_roles.module	(Revision 470)
+++ og_user_roles.module	(Revision 471)
@@ -444,17 +444,22 @@
       break;
 
     case 'insert':
-      if (!empty($node->og_user_roles_default_role) && og_is_group_type($node->type)) {
+      if (isset($node->og_user_roles_default_role) && og_is_group_type($node->type)) {
         db_query("INSERT INTO {og_users_roles_group} (gid, default_role) VALUES (%d, %d)", $node->nid, $node->og_user_roles_default_role);
       }
       break;
 
     case 'update':
-      if (!empty($node->og_user_roles_default_role) && og_is_group_type($node->type)) {
-        db_query("UPDATE {og_users_roles_group} SET default_role = %d WHERE gid = %d", $node->og_user_roles_default_role, $node->nid);
-        if (!db_affected_rows()) {
-          db_query("INSERT INTO {og_users_roles_group} (gid, default_role) VALUES (%d, %d)", $node->nid, $node->og_user_roles_default_role);
+      if (isset($node->og_user_roles_default_role) && og_is_group_type($node->type)) {
+        if ($node->og_user_roles_default_role == 0) {
+          db_query("DELETE FROM {og_users_roles_group} WHERE gid = %d", $node->nid);
         }
+        else {
+          db_query("UPDATE {og_users_roles_group} SET default_role = %d WHERE gid = %d", $node->og_user_roles_default_role, $node->nid);
+          if (!db_affected_rows()) {
+            db_query("INSERT INTO {og_users_roles_group} (gid, default_role) VALUES (%d, %d)", $node->nid, $node->og_user_roles_default_role);
+          }
+        }
       }
       break;