diff --git a/sql/mysql/upgrade/3.5.2/document_transactions.sql b/sql/mysql/upgrade/3.5.2/document_transactions.sql
index 031a970..fef9616 100644
--- a/sql/mysql/upgrade/3.5.2/document_transactions.sql
+++ b/sql/mysql/upgrade/3.5.2/document_transactions.sql
@@ -1,6 +1,6 @@
 alter table document_transactions change version version float default NULL;
 alter table document_transactions change ip ip varchar(15);
-alter table document_transactions change filename filename mediumtext NOT NULL default '';
-alter table document_transactions change comment comment mediumtext NOT NULL default '';
+alter table document_transactions change filename filename mediumtext NOT NULL;
+alter table document_transactions change comment comment mediumtext NOT NULL;
 alter table document_transactions change transaction_namespace transaction_namespace varchar(255);
 alter table document_transactions add index (`datetime`,`transaction_namespace`);
\ No newline at end of file