diff --git a/packages/mui-material/src/Autocomplete/Autocomplete.d.ts b/packages/mui-material/src/Autocomplete/Autocomplete.d.ts
index 48eac3e2ba5d5f..cf789850d12d9c 100644
--- a/packages/mui-material/src/Autocomplete/Autocomplete.d.ts
+++ b/packages/mui-material/src/Autocomplete/Autocomplete.d.ts
@@ -65,7 +65,7 @@ export interface AutocompleteRenderOptionState {
 }
 
 export interface AutocompleteRenderGroupParams {
-  key: string;
+  key: number;
   group: string;
   children?: React.ReactNode;
 }