diff --git a/packages/fiber/src/three-types.ts b/packages/fiber/src/three-types.ts
index 5cd2ba0f0c..9c27cd80a1 100644
--- a/packages/fiber/src/three-types.ts
+++ b/packages/fiber/src/three-types.ts
@@ -2,7 +2,7 @@ import * as THREE from 'three'
 import { EventHandlers } from './core/events'
 import { AttachType } from './core/renderer'
 
-export type NonFunctionKeys<T> = { [K in keyof T]: T[K] extends Function ? never : K }[keyof T]
+export type NonFunctionKeys<T> = { [K in keyof T]-?: T[K] extends Function ? never : K }[keyof T]
 export type Overwrite<T, O> = Omit<T, NonFunctionKeys<O>> & O
 
 /**