diff --git a/packages/mui-styled-engine/src/index.d.ts b/packages/mui-styled-engine/src/index.d.ts
index 9ca475e7b46eb3..1130164844f7b0 100644
--- a/packages/mui-styled-engine/src/index.d.ts
+++ b/packages/mui-styled-engine/src/index.d.ts
@@ -31,8 +31,13 @@ export type CSSProperties = CSS.PropertiesFallback<number | string>;
 export type CSSPropertiesWithMultiValues = {
   [K in keyof CSSProperties]: CSSProperties[K] | Array<Extract<CSSProperties[K], string>>;
 };
+
+// TODO v6 - check if we can drop the unknown, as it breaks the autocomplete
+// For more info on why it was added, see https://github.com/mui/material-ui/pull/26228
 export type CSSPseudos = { [K in CSS.Pseudos]?: unknown | CSSObject };
 
+// TODO v6 - check if we can drop the unknown, as it breaks the autocomplete
+// For more info on why it was added, see https://github.com/mui/material-ui/pull/26228
 export interface CSSOthersObject {
   [propertiesName: string]: unknown | CSSInterpolation;
 }