diff --git a/build.sbt b/build.sbt
index 68243979d9..d5023377bf 100644
--- a/build.sbt
+++ b/build.sbt
@@ -379,7 +379,7 @@ lazy val kernel = crossProject(JSPlatform, JVMPlatform, NativePlatform)
     libraryDependencies += "org.scala-js" %%% "scala-js-macrotask-executor" % MacrotaskExecutorVersion % Test
   )
   .nativeSettings(
-    libraryDependencies += "io.github.cquiroz" %%% "scala-java-time" % "2.4.0"
+    libraryDependencies += "io.github.cquiroz" %%% "scala-java-time" % "2.5.0"
   )
 
 /**
diff --git a/core/shared/src/main/scala/cats/effect/IO.scala b/core/shared/src/main/scala/cats/effect/IO.scala
index 0b726b491b..43a9b3915d 100644
--- a/core/shared/src/main/scala/cats/effect/IO.scala
+++ b/core/shared/src/main/scala/cats/effect/IO.scala
@@ -1188,7 +1188,7 @@ object IO extends IOCompanionPlatform with IOLowPriorityImplicits {
         G.uncancelable { poll =>
           lift(k(resume)) flatMap {
             case Some(fin) => G.onCancel(poll(get), lift(fin))
-            case None => poll(get)
+            case None => get
           }
         }
       }
@@ -1238,7 +1238,7 @@ object IO extends IOCompanionPlatform with IOLowPriorityImplicits {
   def async_[A](k: (Either[Throwable, A] => Unit) => Unit): IO[A] = {
     val body = new Cont[IO, A, A] {
       def apply[G[_]](implicit G: MonadCancel[G, Throwable]) = { (resume, get, lift) =>
-        G.uncancelable { poll => lift(IO.delay(k(resume))).flatMap(_ => poll(get)) }
+        G.uncancelable(_ => lift(IO.delay(k(resume))).flatMap(_ => get))
       }
     }
 
diff --git a/core/shared/src/main/scala/cats/effect/IOFiber.scala b/core/shared/src/main/scala/cats/effect/IOFiber.scala
index 93996e4e2e..d5cbdbe159 100644
--- a/core/shared/src/main/scala/cats/effect/IOFiber.scala
+++ b/core/shared/src/main/scala/cats/effect/IOFiber.scala
@@ -172,7 +172,7 @@ private final class IOFiber[A](
       val handle = registerListener(oc => cb(Right(oc)))
 
       if (handle == null)
-        None /* we were already invoked, so no `CallbackStack` needs to be managed */
+        Some(IO.unit) /* we were already invoked, so no `CallbackStack` needs to be managed */
       else
         Some(IO(handle.clearCurrent()))
     }
diff --git a/kernel/shared/src/main/scala/cats/effect/kernel/Async.scala b/kernel/shared/src/main/scala/cats/effect/kernel/Async.scala
index fab8e244aa..c042060bdb 100644
--- a/kernel/shared/src/main/scala/cats/effect/kernel/Async.scala
+++ b/kernel/shared/src/main/scala/cats/effect/kernel/Async.scala
@@ -94,7 +94,7 @@ trait Async[F[_]] extends AsyncPlatform[F] with Sync[F] with Temporal[F] {
           lift(k(resume)) flatMap {
             case Right(a) => G.pure(a)
             case Left(Some(fin)) => G.onCancel(poll(get), lift(fin))
-            case Left(None) => poll(get)
+            case Left(None) => get
           }
         }
       }
@@ -156,7 +156,7 @@ trait Async[F[_]] extends AsyncPlatform[F] with Sync[F] with Temporal[F] {
    * Polymorphic so it can be used in situations where an arbitrary effect is expected eg
    * [[Fiber.joinWithNever]]
    */
-  def never[A]: F[A] = async(_ => pure(none[F[Unit]]))
+  def never[A]: F[A] = async(_ => pure(Some(unit)))
 
   /**
    * Shift execution of the effect `fa` to the execution context `ec`. Execution is shifted back
diff --git a/kernel/shared/src/main/scala/cats/effect/kernel/Ref.scala b/kernel/shared/src/main/scala/cats/effect/kernel/Ref.scala
index 2b820b5f9c..8f2f9211f1 100644
--- a/kernel/shared/src/main/scala/cats/effect/kernel/Ref.scala
+++ b/kernel/shared/src/main/scala/cats/effect/kernel/Ref.scala
@@ -104,6 +104,11 @@ abstract class Ref[F[_], A] extends RefSource[F, A] with RefSink[F, A] {
    */
   def modify[B](f: A => (A, B)): F[B]
 
+  /**
+   * Like `modify` but the evaluation of the return value is wrapped in the effect type `F`.
+   */
+  def flatModify[B](f: A => (A, F[B]))(implicit F: FlatMap[F]): F[B] = F.flatten(modify(f))
+
   /**
    * Update the value of this ref with a state computation.
    *
diff --git a/kernel/shared/src/main/scala/cats/effect/kernel/Resource.scala b/kernel/shared/src/main/scala/cats/effect/kernel/Resource.scala
index 209b6a8e18..a0ec36a46f 100644
--- a/kernel/shared/src/main/scala/cats/effect/kernel/Resource.scala
+++ b/kernel/shared/src/main/scala/cats/effect/kernel/Resource.scala
@@ -996,23 +996,22 @@ object Resource extends ResourceFOInstances0 with ResourceHOInstances0 with Reso
               val nt2 = new (Resource[F, *] ~> D) {
                 def apply[A](rfa: Resource[F, A]) =
                   Kleisli { r =>
-                    nt(rfa.allocatedCase) flatMap {
-                      case (a, fin) =>
-                        r.update(f => (ec: ExitCase) => f(ec) !> (F.unit >> fin(ec))).as(a)
+                    G uncancelable { poll =>
+                      poll(nt(rfa.allocatedCase)) flatMap {
+                        case (a, fin) =>
+                          r.update(f => (ec: ExitCase) => f(ec) !> (F.unit >> fin(ec))).as(a)
+                      }
                     }
                   }
               }
 
-              for {
-                r <- nt(F.ref((_: ExitCase) => F.unit).map(_.mapK(nt)))
-
-                a <- G.guaranteeCase(body[D].apply(cb, Kleisli.liftF(ga), nt2).run(r)) {
+              nt(F.ref((_: ExitCase) => F.unit).map(_.mapK(nt))) flatMap { r =>
+                G.guaranteeCase(
+                  (body[D].apply(cb, Kleisli.liftF(ga), nt2).run(r), r.get).tupled) {
                   case Outcome.Succeeded(_) => G.unit
                   case oc => r.get.flatMap(fin => nt(fin(ExitCase.fromOutcome(oc))))
                 }
-
-                fin <- r.get
-              } yield (a, fin)
+              }
             }
           }
         }
diff --git a/laws/shared/src/main/scala/cats/effect/laws/AsyncLaws.scala b/laws/shared/src/main/scala/cats/effect/laws/AsyncLaws.scala
index cfddeba102..2aff62f13f 100644
--- a/laws/shared/src/main/scala/cats/effect/laws/AsyncLaws.scala
+++ b/laws/shared/src/main/scala/cats/effect/laws/AsyncLaws.scala
@@ -61,7 +61,7 @@ trait AsyncLaws[F[_]] extends GenTemporalLaws[F, Throwable] with SyncLaws[F] {
     F.async[A](k => F.delay(k(Left(e))) >> F.pure(Some(fu))) <-> F.raiseError(e)
 
   def neverIsDerivedFromAsync[A] =
-    F.never[A] <-> F.async[A](_ => F.pure(None))
+    F.never[A] <-> F.async[A](_ => F.pure(Some(F.unit)))
 
   def executionContextCommutativity[A](fa: F[A]) =
     (fa *> F.executionContext) <-> (F.executionContext <* fa)
diff --git a/project/plugins.sbt b/project/plugins.sbt
index 95a6d5eb8f..6bfb4a02c6 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -4,7 +4,7 @@ addSbtPlugin("org.typelevel" % "sbt-typelevel" % "0.5.0-M6")
 
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.11.0")
 addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.2.0")
-addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.4.7")
+addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.4.9")
 addSbtPlugin("org.portable-scala" % "sbt-scala-native-crossproject" % "1.2.0")
 addSbtPlugin("pl.project13.scala" % "sbt-jmh" % "0.4.3")
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.4.6")
diff --git a/tests/shared/src/test/scala/cats/effect/ResourceSpec.scala b/tests/shared/src/test/scala/cats/effect/ResourceSpec.scala
index af9f0b1619..9a769dd211 100644
--- a/tests/shared/src/test/scala/cats/effect/ResourceSpec.scala
+++ b/tests/shared/src/test/scala/cats/effect/ResourceSpec.scala
@@ -1074,7 +1074,7 @@ class ResourceSpec extends BaseSpec with ScalaCheck with Discipline {
       "Resource[IO, *]",
       AsyncTests[Resource[IO, *]].async[Int, Int, Int](10.millis)
     ) /*(Parameters(seed =
-      Some(Seed.fromBase64("75d9nzLIEobZ3mfn0DvzUkMv-Jt7o7IyQyIvjqwkeVJ=").get)))*/
+      Some(Seed.fromBase64("0FaZxJyh_xN_NL3i_y7bNaLpaWuhO9qUPXmfxxgLIIN=").get)))*/
   }
 
   {