diff --git a/src/lib/types.ts b/src/lib/types.ts
index c3906b39..e49882ae 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -77,7 +77,12 @@ export const postgresColumnUpdateSchema = Type.Object({
   is_nullable: Type.Optional(Type.Boolean()),
   is_unique: Type.Optional(Type.Boolean()),
   comment: Type.Optional(Type.String()),
-  check: Type.Optional(Type.Union([Type.String(), Type.Null()])),
+  check: Type.Optional(
+    Type.Union(
+      // Type.Null() must go first: https://github.com/sinclairzx81/typebox/issues/546
+      [Type.Null(), Type.String()]
+    )
+  ),
 })
 export type PostgresColumnUpdate = Static<typeof postgresColumnUpdateSchema>
 
diff --git a/test/lib/columns.ts b/test/lib/columns.ts
index ef94618c..f16402c7 100644
--- a/test/lib/columns.ts
+++ b/test/lib/columns.ts
@@ -933,3 +933,17 @@ test('column with multiple checks', async () => {
 
   await pgMeta.query(`drop table t`)
 })
+
+test('dropping column checks', async () => {
+  await pgMeta.query(`create table public.t(c int8 check (c != 0))`)
+
+  let res = await pgMeta.columns.retrieve({
+    schema: 'public',
+    table: 't',
+    name: 'c',
+  })
+  res = await pgMeta.columns.update(res.data!.id, { check: null })
+  expect(res?.data?.check).toMatchInlineSnapshot(`null`)
+
+  await pgMeta.query(`drop table t`)
+})