diff --git a/backend/src/utils/typeUtils.ts b/backend/src/utils/typeUtils.ts
index f206795d..619f6cec 100644
--- a/backend/src/utils/typeUtils.ts
+++ b/backend/src/utils/typeUtils.ts
@@ -3,5 +3,6 @@ export type Tail<T extends any[]> = ((...t: T) => void) extends (h: any, ...r: i
 
 export declare type WithRequiredProps<T, K extends keyof T> = T &
   {
+    // https://mariusschulz.com/blog/mapped-type-modifiers-in-typescript#removing-the-mapped-type-modifier
     [PK in K]-?: Exclude<T[K], null>;
   };