diff --git a/src/main/java/io/reactivex/rxjava3/core/Observable.java b/src/main/java/io/reactivex/rxjava3/core/Observable.java
index 18534eecc7..9869276b12 100644
--- a/src/main/java/io/reactivex/rxjava3/core/Observable.java
+++ b/src/main/java/io/reactivex/rxjava3/core/Observable.java
@@ -10371,7 +10371,7 @@ public final <R> Observable<R> lift(@NonNull ObservableOperator<? extends R, ? s
     @CheckReturnValue
     @SchedulerSupport(SchedulerSupport.NONE)
     @NonNull
-    public final <R> Observable<R> map(@NonNull Function<? super T, ? extends R> mapper) {
+    public final <@NonNull R> Observable<R> map(@NonNull Function<? super T, ? extends R> mapper) {
         Objects.requireNonNull(mapper, "mapper is null");
         return RxJavaPlugins.onAssembly(new ObservableMap<>(this, mapper));
     }