diff --git a/src/array.ts b/src/array.ts
index a0a080c6..d51b7d55 100644
--- a/src/array.ts
+++ b/src/array.ts
@@ -8,7 +8,7 @@ import { isArray, isFunction } from './typed'
 export const group = <T, Key extends string | number | symbol>(
   array: readonly T[],
   getGroupId: (item: T) => Key
-): Partial<Record<Key, T[]>> => {
+): Record<Key, T[]> => {
   return array.reduce((acc, item) => {
     const groupId = getGroupId(item)
     if (!acc[groupId]) acc[groupId] = []