diff --git a/core/shared/src/test/scala/fs2/StreamCombinatorsSuite.scala b/core/shared/src/test/scala/fs2/StreamCombinatorsSuite.scala
index d541561a88..fb49f21339 100644
--- a/core/shared/src/test/scala/fs2/StreamCombinatorsSuite.scala
+++ b/core/shared/src/test/scala/fs2/StreamCombinatorsSuite.scala
@@ -1476,27 +1476,35 @@ class StreamCombinatorsSuite extends Fs2Suite {
 
   group("withTimeout") {
     test("timeout never-ending stream") {
-      Stream.never[IO].timeout(100.millis).intercept[TimeoutException]
+      TestControl.executeEmbed {
+        Stream.never[IO].timeout(100.millis).intercept[TimeoutException]
+      }
     }
 
     test("not trigger timeout on successfully completed stream") {
-      Stream.sleep[IO](10.millis).timeout(1.second).compile.drain
+      TestControl.executeEmbed {
+        Stream.sleep[IO](10.millis).timeout(1.second).compile.drain
+      }
     }
 
     test("compose timeouts d1 and d2 when d1 < d2") {
-      val d1 = 20.millis
-      val d2 = 30.millis
-      (Stream.sleep[IO](10.millis).timeout(d1) ++ Stream.sleep[IO](30.millis))
-        .timeout(d2)
-        .intercept[TimeoutException]
+      TestControl.executeEmbed {
+        val d1 = 20.millis
+        val d2 = 30.millis
+        (Stream.sleep[IO](10.millis).timeout(d1) ++ Stream.sleep[IO](30.millis))
+          .timeout(d2)
+          .intercept[TimeoutException]
+      }
     }
 
     test("compose timeouts d1 and d2 when d1 > d2") {
-      val d1 = 40.millis
-      val d2 = 30.millis
-      (Stream.sleep[IO](10.millis).timeout(d1) ++ Stream.sleep[IO](25.millis))
-        .timeout(d2)
-        .intercept[TimeoutException]
+      TestControl.executeEmbed {
+        val d1 = 40.millis
+        val d2 = 30.millis
+        (Stream.sleep[IO](10.millis).timeout(d1) ++ Stream.sleep[IO](25.millis))
+          .timeout(d2)
+          .intercept[TimeoutException]
+      }
     }
   }
 
diff --git a/io/js/src/main/scala/fs2/io/ioplatform.scala b/io/js/src/main/scala/fs2/io/ioplatform.scala
index f9d1805d4f..7086ef2be7 100644
--- a/io/js/src/main/scala/fs2/io/ioplatform.scala
+++ b/io/js/src/main/scala/fs2/io/ioplatform.scala
@@ -120,7 +120,9 @@ private[fs2] trait ioplatform {
             .concurrently(
               Stream.eval(
                 F.async_[Unit](cb =>
-                  duplex.end(e => cb(e.toLeft(()).leftMap(js.JavaScriptException)))
+                  duplex.end { e =>
+                    cb(e.filterNot(_ == null).toLeft(()).leftMap(js.JavaScriptException))
+                  }
                 )
               )
             )
@@ -164,8 +166,11 @@ private[fs2] trait ioplatform {
             if (endAfterUse)
               Stream.exec {
                 F.async[Unit] { cb =>
-                  F.delay(writable.end(e => cb(e.toLeft(()).leftMap(js.JavaScriptException))))
-                    .as(Some(F.unit))
+                  F.delay(
+                    writable.end(e =>
+                      cb(e.filterNot(_ == null).toLeft(()).leftMap(js.JavaScriptException))
+                    )
+                  ).as(Some(F.unit))
                 }
               }
             else Stream.empty