diff --git a/types/test/v3/define-component-test.tsx b/types/test/v3/define-component-test.tsx
index 42d0f32eb0d..481a2d11ac7 100644
--- a/types/test/v3/define-component-test.tsx
+++ b/types/test/v3/define-component-test.tsx
@@ -1165,3 +1165,7 @@ defineComponent({
     return h('div', {}, [...this.$slots.default!])
   }
 })
+
+// #12742 allow attaching custom properties (consistent with v3)
+const Foo = defineComponent({})
+Foo.foobar = 123
diff --git a/types/v3-component-options.d.ts b/types/v3-component-options.d.ts
index d8c64ab13ab..e2da34e753f 100644
--- a/types/v3-component-options.d.ts
+++ b/types/v3-component-options.d.ts
@@ -88,6 +88,9 @@ export interface ComponentOptionsBase<
       'data' | 'computed' | 'methods' | 'setup' | 'props' | 'mixins' | 'extends'
     >,
     ComponentCustomOptions {
+  // allow any options
+  [key: string]: any
+
   // rewrite options api types
   data?: (
     this: CreateComponentPublicInstance<Props, {}, {}, {}, M, Mixin, Extends>,