diff --git a/types/mithril/stream/index.d.ts b/types/mithril/stream/index.d.ts
index f299a3ea11..62684fe448 100644
--- a/types/mithril/stream/index.d.ts
+++ b/types/mithril/stream/index.d.ts
@@ -5,9 +5,7 @@ declare namespace Stream {
 		/** Sets the value of the stream. */
 		(value: T): this;
 		/** Creates a dependent stream whose value is set to the result of the callback function. */
-		map(f: (current: T) => Stream<T> | T | void): Stream<T>;
-		/** Creates a dependent stream whose value is set to the result of the callback function. */
-		map<U>(f: (current: T) => Stream<U> | U): Stream<U>;
+        map<U>(f: (current: T) => U): Stream<U>;
 		/** This method is functionally identical to stream. It exists to conform to Fantasy Land's Applicative specification. */
 		of(val?: T): Stream<T>;
 		/** Apply. */
diff --git a/types/mithril/test/test-stream.ts b/types/mithril/test/test-stream.ts
index ff86d62211..85d76252bb 100644
--- a/types/mithril/test/test-stream.ts
+++ b/types/mithril/test/test-stream.ts
@@ -204,6 +204,13 @@ import { Stream } from 'mithril/stream';
 	console.assert(doubled() === 4);
 }
 
+{
+    const s = stream("a");
+    const t = s.map(() => 1);
+    const n = t() + 1;
+    console.assert(n === 2);
+}
+
 // scan
 
 {