diff --git a/packages/vitest/src/integrations/spy.ts b/packages/vitest/src/integrations/spy.ts
index e69d67a9f79a..076d70e649bb 100644
--- a/packages/vitest/src/integrations/spy.ts
+++ b/packages/vitest/src/integrations/spy.ts
@@ -37,6 +37,8 @@ type Classes<T> = {
 }[keyof T] & (string | symbol)
 
 export interface SpyInstance<TArgs extends any[] = any[], TReturns = any> {
+  (...args: TArgs): TReturns
+
   getMockName(): string
   mockName(n: string): this
   mock: SpyContext<TArgs, TReturns>