diff --git a/misc/db_schema.yaml b/misc/db_schema.yaml
index 2eedd99250..95a889e970 100644
--- a/misc/db_schema.yaml
+++ b/misc/db_schema.yaml
@@ -571,7 +571,7 @@ graph_types:
     graph_descr: { Field: graph_descr, Type: varchar(255), 'Null': true, Default: 'NULL', Extra: '' }
     graph_order: { Field: graph_order, Type: int(11), 'Null': false, Default: 'NULL', Extra: '' }
     graph_section: { Field: graph_section, Type: varchar(32), 'Null': false, Default: 'NULL', Extra: '' }
-    graph_subtype: { Field: graph_subtype, Type: varchar(64), 'Null': false, Default: '', Extra: '' }
+    graph_subtype: { Field: graph_subtype, Type: varchar(64), 'Null': false, Default: 'NULL', Extra: '' }
     graph_type: { Field: graph_type, Type: varchar(32), 'Null': false, Default: 'NULL', Extra: '' }
   Indexes:
     PRIMARY: { Name: PRIMARY, Columns: [graph_type, graph_subtype, graph_section], Unique: true, Type: BTREE }
diff --git a/sql-schema/206.sql b/sql-schema/206.sql
new file mode 100644
index 0000000000..a41c6052a1
--- /dev/null
+++ b/sql-schema/206.sql
@@ -0,0 +1 @@
+ALTER TABLE `graph_types` CHANGE `graph_subtype` `graph_subtype` varchar(64) NOT NULL;