diff --git a/types/index.d.ts b/types/index.d.ts
index df1a587..506a2b7 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -1,7 +1,17 @@
 declare module '@nx-js/observer-util' {
-  function observable<Observable extends object>(obj?: Observable): Observable
+  class ObservableBrand {
+        protected __OBSERVABLE_NOMINAL_BRAND: never;
+  }
+
+  type Observed<T> = T & ObservableBrand;
+
+  type MonoObserved<T> = T extends Observed<infer U>
+    ? MonoObserved<U>
+    : T;
+
+  function observable<Observable extends object>(obj?: Observable): Observed<MonoObserved<Observable>>
   function isObservable(obj: object): boolean
-  function raw<Observable extends object>(obj: Observable): Observable
+  function raw<Observable extends object>(obj: Observable): Observable extends Observed<infer T> ? MonoObserved<T> : Observable;
 
   interface Scheduler {
     add: Function