diff --git a/src/_internal/types.ts b/src/_internal/types.ts
index f3cdba5ed..b65b1ab08 100644
--- a/src/_internal/types.ts
+++ b/src/_internal/types.ts
@@ -439,10 +439,24 @@ export interface ScopedMutator {
  * @typeParam Data - The type of the data related to the key
  * @typeParam MutationData - The type of the data returned by the mutator
  */
-export type KeyedMutator<Data> = <MutationData = Data>(
-  data?: Data | Promise<Data | undefined> | MutatorCallback<Data>,
-  opts?: boolean | MutatorOptions<Data, MutationData>
-) => Promise<Data | MutationData | undefined>
+export type KeyedMutator<Data> = {
+  (
+    data?: Data | Promise<Data | undefined> | MutatorCallback<Data>,
+    opts?: boolean | MutatorOptions<Data, Data>
+  ): Promise<Data | undefined>
+  <MutationData = Data>(
+    data:
+      | MutationData
+      | Promise<MutationData | undefined>
+      | MutatorCallback<MutationData>,
+    opts: Omit<MutatorOptions<Data, MutationData>, 'populateCache'> & {
+      populateCache: (
+        result: MutationData,
+        currentData: Data | undefined
+      ) => Data
+    }
+  ): Promise<Data | MutationData | undefined>
+}
 
 export type SWRConfiguration<
   Data = any,
diff --git a/src/infinite/index.ts b/src/infinite/index.ts
index f410b5bef..7c4204874 100644
--- a/src/infinite/index.ts
+++ b/src/infinite/index.ts
@@ -19,7 +19,6 @@ import {
 import type {
   BareFetcher,
   SWRHook,
-  MutatorCallback,
   Middleware,
   GlobalState
 } from '../_internal'
@@ -238,16 +237,9 @@ export const infinite = (<Data, Error>(useSWRNext: SWRHook) =>
       config
     )
 
-    const mutate = useCallback(
+    const mutate = useCallback<SWRInfiniteKeyedMutator<Data[]>>(
       // eslint-disable-next-line func-names
-      function <T = Data[]>(
-        data?:
-          | undefined
-          | Data[]
-          | Promise<Data[] | undefined>
-          | MutatorCallback<Data[]>,
-        opts?: undefined | boolean | SWRInfiniteMutatorOptions<Data[], T>
-      ) {
+      function (data?: any, opts?: any) {
         // When passing as a boolean, it's explicitly used to disable/enable
         // revalidation.
         const options =
diff --git a/src/infinite/types.ts b/src/infinite/types.ts
index 4237b6aba..2c5204d6c 100644
--- a/src/infinite/types.ts
+++ b/src/infinite/types.ts
@@ -47,10 +47,27 @@ interface SWRInfiniteRevalidateFn<Data = any> {
   (data: Data, key: Arguments): boolean
 }
 
-export type SWRInfiniteKeyedMutator<Data> = <MutationData = Data>(
-  data?: Data | Promise<Data | undefined> | MutatorCallback<Data>,
-  opts?: boolean | SWRInfiniteMutatorOptions<Data, MutationData>
-) => Promise<Data | MutationData | undefined>
+export type SWRInfiniteKeyedMutator<Data> = {
+  (
+    data?: Data | Promise<Data | undefined> | MutatorCallback<Data>,
+    opts?: boolean | SWRInfiniteMutatorOptions<Data, Data>
+  ): Promise<Data | undefined>
+  <MutationData = Data>(
+    data:
+      | MutationData
+      | Promise<MutationData | undefined>
+      | MutatorCallback<MutationData>,
+    opts: Omit<
+      SWRInfiniteMutatorOptions<Data, MutationData>,
+      'populateCache'
+    > & {
+      populateCache: (
+        result: MutationData,
+        currentData: Data | undefined
+      ) => Data
+    }
+  ): Promise<Data | MutationData | undefined>
+}
 
 export interface SWRInfiniteMutatorOptions<Data = any, MutationData = Data>
   extends Omit<MutatorOptions<Data, MutationData>, 'revalidate'> {