diff --git a/spec/operators/dematerialize-spec.ts b/spec/operators/dematerialize-spec.ts
index ed37da9c0b..0fc114200f 100644
--- a/spec/operators/dematerialize-spec.ts
+++ b/spec/operators/dematerialize-spec.ts
@@ -50,7 +50,7 @@ describe('dematerialize operator', () => {
   });
 
   it('should dematerialize a sad stream', () => {
-    const values = {
+    const values: Record<string, Notification<string | undefined>> = {
       a: Notification.createNext('w'),
       b: Notification.createNext('x'),
       c: Notification.createNext('y'),