diff --git a/packages/core/database/src/fields/belongs-to-many-field.ts b/packages/core/database/src/fields/belongs-to-many-field.ts
index e7fed468c..dab447c7a 100644
--- a/packages/core/database/src/fields/belongs-to-many-field.ts
+++ b/packages/core/database/src/fields/belongs-to-many-field.ts
@@ -30,9 +30,11 @@ export class BelongsToManyField extends RelationField {
   references(association): Reference[] {
     const db = this.context.database;
 
+    const onDelete = this.options.onDelete || 'CASCADE';
+
     return [
-      BelongsToField.toReference(db, association.toSource, this.options.onDelete),
-      BelongsToField.toReference(db, association.toTarget, this.options.onDelete),
+      BelongsToField.toReference(db, association.toSource, onDelete),
+      BelongsToField.toReference(db, association.toTarget, onDelete),
     ];
   }