diff --git a/.scala-steward.conf b/.scala-steward.conf
index 291249d..577d69d 100644
--- a/.scala-steward.conf
+++ b/.scala-steward.conf
@@ -4,7 +4,7 @@ updates.ignore = [
   {groupId = "org.scala-lang", artifactId = "scala-compiler", version = "3."}
 ]
 updates.pin = [
-  {groupId = "org.scala-lang", artifactId = "scala3-library", version = "3.3."},
-  {groupId = "org.scala-lang", artifactId = "scala3-library_sjs1", version = "3.3."},
+  {groupId = "org.scala-lang", artifactId = "scala3-library", version = "3.9."},
+  {groupId = "org.scala-lang", artifactId = "scala3-library_sjs1", version = "3.9."},
   {groupId = "com.typesafe.akka", version = "2.6."}
 ]
diff --git a/README.md b/README.md
index 254b664..3b135a3 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ Add the following dependency:
 "com.softwaremill.sttp.shared" %% "core" % "1.5.3"
 ```
 
-sttp-shared is available for Scala 2.12, 2.13, 3.3, Scala.JS and Scala Native.
+sttp-shared is available for Scala 2.12, 2.13, 3.9, Scala.JS and Scala Native.
 
 ### Building & testing the scala-native version
 
diff --git a/build.sbt b/build.sbt
index 6df47ae..371bfe5 100644
--- a/build.sbt
+++ b/build.sbt
@@ -7,7 +7,7 @@ val scala2_12 = "2.12.21"
 val scala2_13 = "2.13.18"
 val scala2 = List(scala2_12, scala2_13)
 val scala2alive = List(scala2_12, scala2_13)
-val scala3 = List("3.3.8")
+val scala3 = List("3.9.0")
 val akkaVersion = "2.6.20"
 val pekkoVersion = "1.7.1"
 val sttpModelVersion = "1.8.2"
@@ -36,7 +36,7 @@ versionScheme := Some("semver-spec")
 
 val commonJvmSettings = Seq(
   scalacOptions ++=
-    (if (ScalaArtifacts.isScala3(scalaVersion.value)) Seq("-Yfuture-lazy-vals", "-java-output-version", "11")
+    (if (ScalaArtifacts.isScala3(scalaVersion.value)) Seq("-java-output-version", "17")
      else Seq("-release", "8")),
   ideSkipProject := (scalaVersion.value != scala2_13),
   bspEnabled := !ideSkipProject.value,
@@ -118,7 +118,8 @@ lazy val core = (projectMatrix in file("core"))
 lazy val ws = (projectMatrix in file("ws"))
   .settings(
     name := "ws",
-    libraryDependencies += "com.softwaremill.sttp.model" %% "core" % sttpModelVersion
+    libraryDependencies += "com.softwaremill.sttp.model" %% "core" % sttpModelVersion,
+    scalacOptions ++= (if (ScalaArtifacts.isScala3(scalaVersion.value)) Nil else Seq("-Xsource:3"))
   )
   .jvmPlatform(
     scalaVersions = scala2 ++ scala3,
diff --git a/ws/src/main/scala/sttp/ws/WebSocket.scala b/ws/src/main/scala/sttp/ws/WebSocket.scala
index 48c5e38..bcc6375 100644
--- a/ws/src/main/scala/sttp/ws/WebSocket.scala
+++ b/ws/src/main/scala/sttp/ws/WebSocket.scala
@@ -46,7 +46,7 @@ trait WebSocket[F[_]] {
     * @param pongOnPing
     *   Should a [[WebSocketFrame.Pong]] be sent when a [[WebSocketFrame.Ping]] is received.
     */
-  def receiveDataFrame(pongOnPing: Boolean = true): F[WebSocketFrame.Data[_]] =
+  def receiveDataFrame(pongOnPing: Boolean = true): F[WebSocketFrame.Data[?]] =
     receive().flatMap {
       case close: WebSocketFrame.Close                => monad.error(WebSocketClosed(Some(close)))
       case d: WebSocketFrame.Data[_]                  => monad.unit(d)
diff --git a/ws/src/test/scala/sttp/ws/testing/WebSocketStubTests.scala b/ws/src/test/scala/sttp/ws/testing/WebSocketStubTests.scala
index 72f4fb2..eddaeb7 100644
--- a/ws/src/test/scala/sttp/ws/testing/WebSocketStubTests.scala
+++ b/ws/src/test/scala/sttp/ws/testing/WebSocketStubTests.scala
@@ -8,14 +8,17 @@ import sttp.ws.{WebSocketClosed, WebSocketFrame}
 
 import scala.util.{Failure, Success}
 import sttp.monad.IdentityMonad
+import sttp.shared.Identity
 
 class WebSocketStubTests extends AnyFlatSpec with Matchers with ScalaFutures {
   class MyException extends Exception
 
+  private implicit val identityMonad: MonadError[Identity] = IdentityMonad
+
   "web socket stub" should "return initial Incoming frames on 'receive'" in {
     val frames = List("a", "b", "c").map(WebSocketFrame.text)
     val webSocketStub = WebSocketStub.initialReceive(frames)
-    val ws = webSocketStub.build(IdentityMonad)
+    val ws = webSocketStub.build[Identity]
 
     ws.receive() shouldBe WebSocketFrame.text("a")
     ws.receive() shouldBe WebSocketFrame.text("b")
@@ -26,7 +29,7 @@ class WebSocketStubTests extends AnyFlatSpec with Matchers with ScalaFutures {
     val okFrame = WebSocketFrame.text("abc")
     val exception = new MyException
     val webSocketStub = WebSocketStub.initialReceiveWith(List(Success(okFrame), Failure(exception)))
-    val ws = webSocketStub.build(IdentityMonad)
+    val ws = webSocketStub.build[Identity]
 
     ws.receive() shouldBe WebSocketFrame.text("abc")
     assertThrows[MyException](ws.receive())
@@ -43,7 +46,7 @@ class WebSocketStubTests extends AnyFlatSpec with Matchers with ScalaFutures {
         case `expectedFrame` => List(secondFrame, thirdFrame)
         case _               => List.empty
       }
-    val ws = webSocketStub.build(IdentityMonad)
+    val ws = webSocketStub.build[Identity]
 
     ws.receive() shouldBe WebSocketFrame.text("No. 1")
     assertThrows[IllegalStateException](ws.receive()) // no more stubbed messages
@@ -60,7 +63,7 @@ class WebSocketStubTests extends AnyFlatSpec with Matchers with ScalaFutures {
 
     val webSocketStub = WebSocketStub.noInitialReceive
       .thenRespondWith(_ => List(Success(ok), Failure(exception)))
-    val ws = webSocketStub.build(IdentityMonad)
+    val ws = webSocketStub.build[Identity]
 
     ws.send(WebSocketFrame.text("let's add responses"))
     ws.receive() shouldBe WebSocketFrame.text("ok")
@@ -71,7 +74,7 @@ class WebSocketStubTests extends AnyFlatSpec with Matchers with ScalaFutures {
     val ok = WebSocketFrame.text("ok")
     val closeFrame = WebSocketFrame.Close(500, "internal error")
     val webSocketStub = WebSocketStub.initialReceive(List(closeFrame, ok))
-    val ws = webSocketStub.build(IdentityMonad)
+    val ws = webSocketStub.build[Identity]
 
     ws.send(WebSocketFrame.text("let's add responses"))
     ws.receive() shouldBe closeFrame
@@ -84,7 +87,7 @@ class WebSocketStubTests extends AnyFlatSpec with Matchers with ScalaFutures {
       .thenRespondS(0) { case (counter, _) =>
         (counter + 1, List(WebSocketFrame.text(s"No. $counter")))
       }
-    val ws = webSocketStub.build(IdentityMonad)
+    val ws = webSocketStub.build[Identity]
 
     ws.send(WebSocketFrame.text("a"))
     ws.send(WebSocketFrame.text("b"))
@@ -115,7 +118,8 @@ class WebSocketStubTests extends AnyFlatSpec with Matchers with ScalaFutures {
 
   "receive" should "be lazy" in {
     // given
-    val ws = WebSocketStub.noInitialReceive.thenRespond(_ => List(WebSocketFrame.text("test"))).build(LazyMonad)
+    implicit val lazyMonad: MonadError[() => *] = LazyMonad
+    val ws = WebSocketStub.noInitialReceive.thenRespond(_ => List(WebSocketFrame.text("test"))).build[() => *]
 
     // when
     val doReceive = ws.receive() // should return a lazy receive