diff --git a/src/_internal/types.ts b/src/_internal/types.ts
index 7a85047a2..f3cdba5ed 100644
--- a/src/_internal/types.ts
+++ b/src/_internal/types.ts
@@ -440,12 +440,9 @@ export interface ScopedMutator {
  * @typeParam MutationData - The type of the data returned by the mutator
  */
 export type KeyedMutator<Data> = <MutationData = Data>(
-  data?:
-    | MutationData
-    | Promise<MutationData | undefined>
-    | MutatorCallback<MutationData>,
+  data?: Data | Promise<Data | undefined> | MutatorCallback<Data>,
   opts?: boolean | MutatorOptions<Data, MutationData>
-) => Promise<MutationData | undefined>
+) => Promise<Data | MutationData | undefined>
 
 export type SWRConfiguration<
   Data = any,
diff --git a/src/infinite/index.ts b/src/infinite/index.ts
index 6e51f8574..f410b5bef 100644
--- a/src/infinite/index.ts
+++ b/src/infinite/index.ts
@@ -240,12 +240,13 @@ export const infinite = (<Data, Error>(useSWRNext: SWRHook) =>
 
     const mutate = useCallback(
       // eslint-disable-next-line func-names
-      function <MutationData = Data[]>(
+      function <T = Data[]>(
         data?:
-          | MutationData
-          | Promise<MutationData | undefined>
-          | MutatorCallback<MutationData>,
-        opts?: boolean | SWRInfiniteMutatorOptions<Data[], MutationData>
+          | undefined
+          | Data[]
+          | Promise<Data[] | undefined>
+          | MutatorCallback<Data[]>,
+        opts?: undefined | boolean | SWRInfiniteMutatorOptions<Data[], T>
       ) {
         // When passing as a boolean, it's explicitly used to disable/enable
         // revalidation.