diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 02e0f5ea8990..f3a7296032d2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -46,7 +46,7 @@ jobs:
       fail-fast: false
       matrix:
         java: ['adopt@1.8', 'adopt@1.11']
-        scala: ['2.11.12', '2.12.13', '2.13.5', '3.0.0-RC3']
+        scala: ['2.11.12', '2.12.13', '2.13.5', '3.0.0']
         platform: ['JVM', 'JS', 'Native']
     steps:
     - name: Checkout current branch
@@ -66,9 +66,9 @@ jobs:
     - name: Test 2.12.x and 2.13.x
       if: ${{ !startsWith(matrix.scala, '2.11.') && !startsWith(matrix.scala, '3.0.') && matrix.platform != 'Native' }}
       run: sbt ++${{ matrix.scala }}! test${{ matrix.platform }}
-    - name: Test 3.x (JVM only)
-      if: ${{ startsWith(matrix.scala, '3.0.') && contains(matrix.java, '1.8') && matrix.platform == 'JVM' }}
-      run: sbt ++${{ matrix.scala }}! testJVMDotty
+    - name: Test 3.x
+      if: ${{ startsWith(matrix.scala, '3.0.') && contains(matrix.java, '1.8') && matrix.platform != 'Native' }}
+      run: sbt ++${{ matrix.scala }}! test${{ matrix.platform }}Dotty
     - name: Test native
       if: ${{ !startsWith(matrix.scala, '3.0.') && matrix.platform == 'Native' }}
       run: sbt ++${{ matrix.scala }}! testNative
diff --git a/build.sbt b/build.sbt
index 602d30e38135..cde65c116972 100644
--- a/build.sbt
+++ b/build.sbt
@@ -56,6 +56,10 @@ addCommandAlias(
   "testJVMDotty",
   ";coreTestsJVM/test;stacktracerJVM/test:compile;streamsTestsJVM/test;testTestsJVM/test;testMagnoliaTestsJVM/test;testRefinedJVM/test;testRunnerJVM/test:run;examplesJVM/test:compile"
 )
+addCommandAlias(
+  "testJSDotty",
+  ";coreTestsJS/test;stacktracerJS/test;streamsTestsJS/test;testTestsJS/test;testRefinedJS/test;examplesJS/test:compile"
+)
 addCommandAlias(
   "testJVM211",
   ";coreTestsJVM/test;stacktracerJVM/test;streamsTestsJVM/test;testTestsJVM/test;testRunnerJVM/test:run;examplesJVM/test:compile;macrosTestsJVM/test"
@@ -126,7 +130,7 @@ lazy val core = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .settings(stdSettings("zio"))
   .settings(crossProjectSettings)
   .settings(buildInfoSettings("zio"))
-  .settings(libraryDependencies += "dev.zio" %%% "izumi-reflect" % "1.1.1")
+  .settings(libraryDependencies += "dev.zio" %%% "izumi-reflect" % "1.1.2")
   .enablePlugins(BuildInfoPlugin)
 
 lazy val coreJVM = core.jvm
@@ -135,6 +139,7 @@ lazy val coreJVM = core.jvm
   .settings(mimaSettings(failOnProblem = true))
 
 lazy val coreJS = core.js
+  .settings(dottySettings)
 
 lazy val coreNative = core.native
   .settings(nativeSettings)
@@ -165,6 +170,7 @@ lazy val coreTestsJVM = coreTests.jvm
   .settings(replSettings)
 
 lazy val coreTestsJS = coreTests.js
+  .settings(dottySettings)
 
 lazy val macros = crossProject(JSPlatform, JVMPlatform)
   .in(file("macros"))
@@ -208,6 +214,7 @@ lazy val streamsJVM = streams.jvm
   .settings(mimaSettings(failOnProblem = false))
 
 lazy val streamsJS = streams.js
+  .settings(dottySettings)
 
 lazy val streamsNative = streams.native
   .settings(nativeSettings)
@@ -232,6 +239,7 @@ lazy val streamsTestsJVM = streamsTests.jvm
   .settings(dottySettings)
 
 lazy val streamsTestsJS = streamsTests.js
+  .settings(dottySettings)
 
 lazy val test = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .in(file("test"))
@@ -252,6 +260,7 @@ lazy val testJVM = test.jvm
   // No bincompat on zio-test yet
   .settings(mimaSettings(failOnProblem = false))
 lazy val testJS = test.js
+  .settings(dottySettings)
   .settings(
     libraryDependencies ++= List(
       "io.github.cquiroz" %%% "scala-java-time"      % "2.3.0",
@@ -275,7 +284,7 @@ lazy val testTests = crossProject(JSPlatform, JVMPlatform)
   .enablePlugins(BuildInfoPlugin)
 
 lazy val testTestsJVM = testTests.jvm.settings(dottySettings)
-lazy val testTestsJS  = testTests.js
+lazy val testTestsJS  = testTests.js.settings(dottySettings)
 
 lazy val testMagnolia = crossProject(JVMPlatform, JSPlatform)
   .in(file("test-magnolia"))
@@ -341,6 +350,7 @@ lazy val testRefined = crossProject(JVMPlatform, JSPlatform)
 lazy val testRefinedJVM = testRefined.jvm
   .settings(dottySettings)
 lazy val testRefinedJS = testRefined.js
+  .settings(dottySettings)
 
 lazy val stacktracer = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .in(file("stacktracer"))
@@ -350,6 +360,7 @@ lazy val stacktracer = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .enablePlugins(BuildInfoPlugin)
 
 lazy val stacktracerJS = stacktracer.js
+  .settings(dottySettings)
 lazy val stacktracerJVM = stacktracer.jvm
   .settings(dottySettings)
   .settings(replSettings)
@@ -370,7 +381,11 @@ lazy val testRunnerJVM = testRunner.jvm
   .settings(dottySettings)
   .settings(libraryDependencies ++= Seq("org.scala-sbt" % "test-interface" % "1.0"))
 lazy val testRunnerJS = testRunner.js
-  .settings(libraryDependencies ++= Seq("org.scala-js" %% "scalajs-test-interface" % scalaJSVersion))
+  .settings(
+    libraryDependencies ++= Seq(
+      ("org.scala-js" %% "scalajs-test-interface" % scalaJSVersion).cross(CrossVersion.for3Use2_13)
+    )
+  )
 lazy val testRunnerNative = testRunner.native
   .settings(nativeSettings)
   .settings(libraryDependencies ++= Seq("org.scala-native" %%% "test-interface" % nativeVersion))
@@ -444,6 +459,7 @@ lazy val examples = crossProject(JVMPlatform, JSPlatform)
   .dependsOn(macros, testRunner)
 
 lazy val examplesJS = examples.js
+  .settings(dottySettings)
 lazy val examplesJVM = examples.jvm
   .settings(dottySettings)
   .dependsOn(testJunitRunnerJVM)
diff --git a/core/js/src/main/scala/zio/TaskPlatformSpecific.scala b/core/js/src/main/scala/zio/TaskPlatformSpecific.scala
index c3255b0b2ade..96ffd363f18d 100644
--- a/core/js/src/main/scala/zio/TaskPlatformSpecific.scala
+++ b/core/js/src/main/scala/zio/TaskPlatformSpecific.scala
@@ -17,7 +17,7 @@
 package zio
 
 import scala.scalajs.js
-import scala.scalajs.js.{Promise => JSPromise}
+import scala.scalajs.js.{Function1, Promise => JSPromise, Thenable, |}
 
 private[zio] trait TaskPlatformSpecific { self: Task.type =>
 
@@ -26,14 +26,16 @@ private[zio] trait TaskPlatformSpecific { self: Task.type =>
    */
   def fromPromiseJS[A](promise: => JSPromise[A]): Task[A] =
     self.effectAsync { callback =>
-      promise.`then`[Unit](
-        a => callback(UIO.succeedNow(a)),
-        js.defined { (e: Any) =>
+      val onFulfilled: Function1[A, Unit | Thenable[Unit]] = new scala.Function1[A, Unit | Thenable[Unit]] {
+        def apply(a: A): Unit | Thenable[Unit] = callback(UIO.succeedNow(a))
+      }
+      val onRejected: Function1[Any, Unit | Thenable[Unit]] = new scala.Function1[Any, Unit | Thenable[Unit]] {
+        def apply(e: Any): Unit | Thenable[Unit] =
           callback(IO.fail(e match {
             case t: Throwable => t
             case _            => js.JavaScriptException(e)
           }))
-        }
-      )
+      }
+      promise.`then`[Unit](onFulfilled, js.defined(onRejected))
     }
 }
diff --git a/core/js/src/main/scala/zio/ZIOPlatformSpecific.scala b/core/js/src/main/scala/zio/ZIOPlatformSpecific.scala
index 74d512664f35..aea716b7855b 100644
--- a/core/js/src/main/scala/zio/ZIOPlatformSpecific.scala
+++ b/core/js/src/main/scala/zio/ZIOPlatformSpecific.scala
@@ -17,7 +17,7 @@
 package zio
 
 import scala.scalajs.js
-import scala.scalajs.js.{Promise => JSPromise}
+import scala.scalajs.js.{Function1, Promise => JSPromise, Thenable, |}
 
 private[zio] trait ZIOPlatformSpecific[-R, +E, +A] { self: ZIO[R, E, A] =>
 
@@ -42,14 +42,16 @@ private[zio] trait ZIOCompanionPlatformSpecific { self: ZIO.type =>
    */
   def fromPromiseJS[A](promise: => JSPromise[A]): Task[A] =
     self.effectAsync { callback =>
-      promise.`then`[Unit](
-        a => callback(UIO.succeedNow(a)),
-        js.defined { (e: Any) =>
+      val onFulfilled: Function1[A, Unit | Thenable[Unit]] = new scala.Function1[A, Unit | Thenable[Unit]] {
+        def apply(a: A): Unit | Thenable[Unit] = callback(UIO.succeedNow(a))
+      }
+      val onRejected: Function1[Any, Unit | Thenable[Unit]] = new scala.Function1[Any, Unit | Thenable[Unit]] {
+        def apply(e: Any): Unit | Thenable[Unit] =
           callback(IO.fail(e match {
             case t: Throwable => t
             case _            => js.JavaScriptException(e)
           }))
-        }
-      )
+      }
+      promise.`then`[Unit](onFulfilled, js.defined(onRejected))
     }
 }