diff --git a/backend/migrations/2_add_colour.sql b/backend/migrations/2_add_colour.sql
index 2381df8..6dcb3bb 100644
--- a/backend/migrations/2_add_colour.sql
+++ b/backend/migrations/2_add_colour.sql
@@ -1,2 +1,2 @@
 alter table allowances
-add column colour integer not null;
+add column colour integer;