diff --git a/sql/mysql/install/structure.sql b/sql/mysql/install/structure.sql
index 878e265..f3f46a3 100644
--- a/sql/mysql/install/structure.sql
+++ b/sql/mysql/install/structure.sql
@@ -483,7 +483,7 @@ CREATE TABLE `documents` (
   `id` int(11) NOT NULL default '0',
   `creator_id` int(11) NOT NULL default '0',
   `modified` datetime NOT NULL default '0000-00-00 00:00:00',
-  `folder_id` int(11) NOT NULL default '0',
+  `folder_id` int(11) default '0',
   `is_checked_out` tinyint(1) NOT NULL default '0',
   `parent_folder_ids` mediumtext,
   `full_path` mediumtext,
diff --git a/sql/mysql/upgrade/3.0.3.6/document-restore.sql b/sql/mysql/upgrade/3.0.3.6/document-restore.sql
index fd782a4..126116b 100644
--- a/sql/mysql/upgrade/3.0.3.6/document-restore.sql
+++ b/sql/mysql/upgrade/3.0.3.6/document-restore.sql
@@ -1,3 +1,2 @@
 ALTER TABLE `documents` ADD `restore_folder_id` INT(11);
 ALTER TABLE `documents` ADD `restore_folder_path` text;
-ALTER TABLE `documents` CHANGE `folder_id` `folder_id` int(11),
\ No newline at end of file
diff --git a/sql/mysql/upgrade/3.1.1/parentless-documents.sql b/sql/mysql/upgrade/3.1.1/parentless-documents.sql
new file mode 100644
index 0000000..3f3cb7c
--- /dev/null
+++ b/sql/mysql/upgrade/3.1.1/parentless-documents.sql
@@ -0,0 +1 @@
+ALTER TABLE `documents` CHANGE `folder_id` `folder_id` int(11);