diff --git a/packages/vite/src/node/config.ts b/packages/vite/src/node/config.ts
index 8c83bf787896ea..19714b192f45bb 100644
--- a/packages/vite/src/node/config.ts
+++ b/packages/vite/src/node/config.ts
@@ -119,6 +119,7 @@ export type UserConfigExport =
  */
 export function defineConfig(config: UserConfig): UserConfig
 export function defineConfig(config: Promise<UserConfig>): Promise<UserConfig>
+export function defineConfig(config: UserConfigFnObject): UserConfigFnObject
 export function defineConfig(config: UserConfigExport): UserConfigExport
 export function defineConfig(config: UserConfigExport): UserConfigExport {
   return config