diff --git a/api/src/database/migrations/20210924A-add-collection-organization.ts b/api/src/database/migrations/20210924A-add-collection-organization.ts
index 5929065ad8..8c41628cc7 100644
--- a/api/src/database/migrations/20210924A-add-collection-organization.ts
+++ b/api/src/database/migrations/20210924A-add-collection-organization.ts
@@ -3,7 +3,7 @@ import { Knex } from 'knex';
 export async function up(knex: Knex): Promise<void> {
 	await knex.schema.alterTable('directus_collections', (table) => {
 		table.integer('sort');
-		table.string('group', 64).references('collection').inTable('directus_collections').onDelete('SET NULL');
+		table.string('group', 64).references('collection').inTable('directus_collections');
 		table.string('collapse').defaultTo('open').notNullable();
 	});
 }
diff --git a/api/src/services/collections.ts b/api/src/services/collections.ts
index 169c55797a..9b897fbe30 100644
--- a/api/src/services/collections.ts
+++ b/api/src/services/collections.ts
@@ -365,6 +365,9 @@ export class CollectionsService {
 		}
 
 		await this.knex.transaction(async (trx) => {
+			// Make sure this collection isn't used as a group in any other collections
+			await trx('directus_collections').update({ group: null }).where({ group: collectionKey });
+
 			if (collectionToBeDeleted!.meta) {
 				const collectionItemsService = new ItemsService('directus_collections', {
 					knex: trx,