diff --git a/project/ScalaVer.scala b/project/ScalaVer.scala
index 70dfe23..6d118dd 100644
--- a/project/ScalaVer.scala
+++ b/project/ScalaVer.scala
@@ -15,7 +15,7 @@ object ScalaVer {
 
   val values: Seq[ScalaVer] = Set(_211, _212, _213, _300).toSeq
 
-  val default: ScalaVer = _212
+  val default: ScalaVer = _300
 
   def fromEnv: Option[ScalaVer] = sys.env.get("SCALA_VER") flatMap fromString
 
diff --git a/src/main/scala/com/github/andyglow/websocket/Websocket.scala b/src/main/scala/com/github/andyglow/websocket/Websocket.scala
index 5343d2d..a1dce24 100644
--- a/src/main/scala/com/github/andyglow/websocket/Websocket.scala
+++ b/src/main/scala/com/github/andyglow/websocket/Websocket.scala
@@ -52,15 +52,19 @@ trait Websocket {
   */
 private[websocket] class WebsocketImpl(ch: Channel) extends Websocket {
 
-  override def ![T: MessageAdapter](msg: T): Unit =
-    ch writeAndFlush { MessageAdapter[T] format msg }
+  override def ![T: MessageAdapter](msg: T): Unit = {
+    ch.writeAndFlush(MessageAdapter[T].format(msg))
+    ()
+  }
 
   override def close()(implicit ec: ExecutionContext): Future[Unit] = {
-    ch writeAndFlush new CloseWebSocketFrame
+    ch.writeAndFlush(new CloseWebSocketFrame)
     val f = NettyFuture(ch.closeFuture())
-    f map { _ => () }
+    f.map { _ => () }
   }
 
-  override def ping()(implicit ec: ExecutionContext): Unit =
+  override def ping()(implicit ec: ExecutionContext): Unit = {
     ch.writeAndFlush(new PingWebSocketFrame())
+    ()
+  }
 }
diff --git a/src/main/scala/com/github/andyglow/websocket/WebsocketClient.scala b/src/main/scala/com/github/andyglow/websocket/WebsocketClient.scala
index eee64c9..b2fa12f 100644
--- a/src/main/scala/com/github/andyglow/websocket/WebsocketClient.scala
+++ b/src/main/scala/com/github/andyglow/websocket/WebsocketClient.scala
@@ -90,6 +90,8 @@ class WebsocketClient[T: MessageAdapter] private (
           new websocketx.WebSocketFrameAggregator(Int.MaxValue),
           nettyHandler
         )
+
+        ()
       }
     }
 
@@ -114,7 +116,10 @@ class WebsocketClient[T: MessageAdapter] private (
 
   /** Runs though shutdown process synchronously
     */
-  def shutdownSync(): Unit = shutdown().syncUninterruptibly()
+  def shutdownSync(): Unit = {
+    shutdown().syncUninterruptibly()
+    ()
+  }
 
   /** Executes shutdown returning Future that is going to be resolved once shutdown process is completed or if error has
     * happened.
diff --git a/src/main/scala/com/github/andyglow/websocket/WebsocketNettyHandler.scala b/src/main/scala/com/github/andyglow/websocket/WebsocketNettyHandler.scala
index 0634b3a..783456f 100644
--- a/src/main/scala/com/github/andyglow/websocket/WebsocketNettyHandler.scala
+++ b/src/main/scala/com/github/andyglow/websocket/WebsocketNettyHandler.scala
@@ -1,14 +1,12 @@
 package com.github.andyglow.websocket
 
 import io.netty.buffer.ByteBufHolder
-import io.netty.channel.ChannelFuture
 import io.netty.channel.ChannelHandlerContext
 import io.netty.channel.ChannelPromise
 import io.netty.channel.SimpleChannelInboundHandler
 import io.netty.handler.codec.http.FullHttpResponse
 import io.netty.handler.codec.http.websocketx._
 import io.netty.util.CharsetUtil
-import scala.annotation.nowarn
 import scala.concurrent.stm._
 import scala.util.control.NonFatal
 
@@ -61,15 +59,18 @@ private[websocket] class WebsocketNettyHandler[T](
 
   override def channelActive(ctx: ChannelHandlerContext): Unit = {
     handshaker.handshake(ctx.channel())
+    ()
   }
 
   override def channelRead0(ctx: ChannelHandlerContext, msg: ByteBufHolder): Unit = {
     val ch = ctx.channel()
-    def controls: PartialFunction[ByteBufHolder, ChannelFuture] = {
+    def controls: PartialFunction[ByteBufHolder, Unit] = {
       case _: CloseWebSocketFrame =>
         try { handler.onClose(()) }
         catch { case NonFatal(ex) => handler.reportFailure(ex) }
         ch.close()
+        ()
+
       case msg: FullHttpResponse =>
         if (!handshaker.isHandshakeComplete) {
           try {
@@ -81,6 +82,7 @@ private[websocket] class WebsocketNettyHandler[T](
             case ex: WebSocketHandshakeException =>
               atomic { implicit txn => handshakeFuture().setFailure(ex) }
           }
+          ()
         } else {
           throw new IllegalStateException(
             s"Unexpected FullHttpResponse (status=${msg.status}, content=${msg.content().toString(CharsetUtil.UTF_8)})"
@@ -92,7 +94,6 @@ private[websocket] class WebsocketNettyHandler[T](
   }
 
   @Override
-  @nowarn
   override def exceptionCaught(ctx: ChannelHandlerContext, cause: Throwable): Unit = {
     ctx.close()
     atomic { implicit txn =>
@@ -100,5 +101,7 @@ private[websocket] class WebsocketNettyHandler[T](
       if (!f.isDone) f.setFailure(cause)
       else handler.reportFailure(cause)
     }
+
+    ()
   }
 }
diff --git a/src/main/scala/com/github/andyglow/websocket/util/NettyFuture.scala b/src/main/scala/com/github/andyglow/websocket/util/NettyFuture.scala
index a6f14c9..ec3a4a9 100644
--- a/src/main/scala/com/github/andyglow/websocket/util/NettyFuture.scala
+++ b/src/main/scala/com/github/andyglow/websocket/util/NettyFuture.scala
@@ -10,13 +10,14 @@ import scala.concurrent.Promise
 object NettyFuture {
 
   def apply[T](f: NFuture[T]): Future[T] = {
-    val p = Promise[T]()
-    val l = new GenericFutureListener[NFuture[T]]() {
+    val promise = Promise[T]()
+    val futureListener = new GenericFutureListener[NFuture[T]]() {
       override def operationComplete(future: NFuture[T]): Unit = {
-        if (future.isSuccess) p.success(future.getNow) else p.failure(future.cause())
+        if (future.isSuccess) promise.success(future.getNow) else promise.failure(future.cause())
+        ()
       }
     }
-    f addListener l
-    p.future
+    f.addListener(futureListener)
+    promise.future
   }
 }
diff --git a/src/test/scala-2.11/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala b/src/test/scala-2.11/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
index bdb7423..f865252 100644
--- a/src/test/scala-2.11/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
+++ b/src/test/scala-2.11/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
@@ -2,6 +2,7 @@ package com.github.andyglow.websocket.testserver
 
 import akka.actor.ActorSystem
 import akka.http.scaladsl.Http
+import akka.http.scaladsl.model.ws.UpgradeToWebSocket
 import akka.http.scaladsl.model.{HttpRequest, HttpResponse}
 import akka.stream.Materializer
 
@@ -9,11 +10,13 @@ import scala.concurrent.Future
 
 trait CrossScalaVersionAkkaApi {
 
-  def launchServer(
+  @inline def launchServer(
     interface: String,
     port: Int,
     handler: HttpRequest => HttpResponse)(implicit system: ActorSystem, mat: Materializer): Future[Http.ServerBinding] = {
 
     Http().bindAndHandleSync(handler, interface, port)
   }
+
+  @inline def websocketAttribution(x: HttpRequest): Option[UpgradeToWebSocket] = x.header[UpgradeToWebSocket]
 }
diff --git a/src/test/scala-2.12/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala b/src/test/scala-2.12/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
index 289c9bb..7f0ee17 100644
--- a/src/test/scala-2.12/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
+++ b/src/test/scala-2.12/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
@@ -2,18 +2,21 @@ package com.github.andyglow.websocket.testserver
 
 import akka.actor.ActorSystem
 import akka.http.scaladsl.Http
-import akka.http.scaladsl.model.{HttpRequest, HttpResponse}
+import akka.http.scaladsl.model.ws.WebSocketUpgrade
+import akka.http.scaladsl.model.{AttributeKeys, HttpRequest, HttpResponse}
 import akka.stream.Materializer
 
 import scala.concurrent.Future
 
 trait CrossScalaVersionAkkaApi {
 
-  def launchServer(
+  @inline def launchServer(
     interface: String,
     port: Int,
     handler: HttpRequest => HttpResponse)(implicit system: ActorSystem, mat: Materializer): Future[Http.ServerBinding] = {
 
     Http().newServerAt(interface, port).bindSync(handler)
   }
+
+  @inline def websocketAttribution(x: HttpRequest): Option[WebSocketUpgrade] = x.attribute(AttributeKeys.webSocketUpgrade)
 }
diff --git a/src/test/scala-2.13/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala b/src/test/scala-2.13/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
index 289c9bb..2624b52 100644
--- a/src/test/scala-2.13/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
+++ b/src/test/scala-2.13/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
@@ -2,7 +2,8 @@ package com.github.andyglow.websocket.testserver
 
 import akka.actor.ActorSystem
 import akka.http.scaladsl.Http
-import akka.http.scaladsl.model.{HttpRequest, HttpResponse}
+import akka.http.scaladsl.model.ws.WebSocketUpgrade
+import akka.http.scaladsl.model.{AttributeKeys, HttpRequest, HttpResponse}
 import akka.stream.Materializer
 
 import scala.concurrent.Future
@@ -16,4 +17,6 @@ trait CrossScalaVersionAkkaApi {
 
     Http().newServerAt(interface, port).bindSync(handler)
   }
+
+  @inline def websocketAttribution(x: HttpRequest): Option[WebSocketUpgrade] = x.attribute(AttributeKeys.webSocketUpgrade)
 }
diff --git a/src/test/scala-3/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala b/src/test/scala-3/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
index 289c9bb..7f0ee17 100644
--- a/src/test/scala-3/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
+++ b/src/test/scala-3/com/github/andyglow/websocket/testserver/CrossScalaVersionAkkaApi.scala
@@ -2,18 +2,21 @@ package com.github.andyglow.websocket.testserver
 
 import akka.actor.ActorSystem
 import akka.http.scaladsl.Http
-import akka.http.scaladsl.model.{HttpRequest, HttpResponse}
+import akka.http.scaladsl.model.ws.WebSocketUpgrade
+import akka.http.scaladsl.model.{AttributeKeys, HttpRequest, HttpResponse}
 import akka.stream.Materializer
 
 import scala.concurrent.Future
 
 trait CrossScalaVersionAkkaApi {
 
-  def launchServer(
+  @inline def launchServer(
     interface: String,
     port: Int,
     handler: HttpRequest => HttpResponse)(implicit system: ActorSystem, mat: Materializer): Future[Http.ServerBinding] = {
 
     Http().newServerAt(interface, port).bindSync(handler)
   }
+
+  @inline def websocketAttribution(x: HttpRequest): Option[WebSocketUpgrade] = x.attribute(AttributeKeys.webSocketUpgrade)
 }
diff --git a/src/test/scala/com/github/andyglow/websocket/WebsocketSpec.scala b/src/test/scala/com/github/andyglow/websocket/WebsocketSpec.scala
index 9e546b7..41bc250 100644
--- a/src/test/scala/com/github/andyglow/websocket/WebsocketSpec.scala
+++ b/src/test/scala/com/github/andyglow/websocket/WebsocketSpec.scala
@@ -1,14 +1,14 @@
 package com.github.andyglow.websocket
 
-import io.netty.buffer.{ByteBuf, ByteBufHolder, Unpooled}
+import io.netty.buffer.{ByteBufHolder, Unpooled}
 import io.netty.channel.{Channel, ChannelFuture}
 import io.netty.handler.codec.http.websocketx.{BinaryWebSocketFrame, CloseWebSocketFrame, PingWebSocketFrame, TextWebSocketFrame}
-import org.scalatest.funsuite.AnyFunSuite
 import org.mockito.Mockito._
 import org.scalactic.source.Position
+import org.scalatest.funsuite.AnyFunSuite
 
 import java.nio.{ByteBuffer, CharBuffer}
-import java.util.concurrent.{ExecutorService, Executors}
+import java.util.concurrent.Executors
 import scala.concurrent.ExecutionContext
 
 class WebsocketSpec extends AnyFunSuite {
@@ -41,7 +41,7 @@ class WebsocketSpec extends AnyFunSuite {
     )
   }
 
-  private def examine(wsRun: Websocket => Unit, verifyRun: Channel => Unit)(implicit pos: Position): Unit = {
+  private def examine(wsRun: Websocket => Any, verifyRun: Channel => Any)(implicit pos: Position): Unit = {
     val ch = mock(classOf[Channel])
     val closeFut = mock(classOf[ChannelFuture])
     when(ch.closeFuture()).thenReturn(closeFut)
@@ -50,6 +50,7 @@ class WebsocketSpec extends AnyFunSuite {
     wsRun(ws)
     try {
       verifyRun(ch)
+      ()
     } catch {
       case th: Throwable => fail(th)
     }
diff --git a/src/test/scala/com/github/andyglow/websocket/testserver/TestServer.scala b/src/test/scala/com/github/andyglow/websocket/testserver/TestServer.scala
index 990defc..26369ca 100644
--- a/src/test/scala/com/github/andyglow/websocket/testserver/TestServer.scala
+++ b/src/test/scala/com/github/andyglow/websocket/testserver/TestServer.scala
@@ -1,11 +1,10 @@
 package com.github.andyglow.websocket.testserver
 
 import akka.actor.ActorSystem
-import akka.http.scaladsl.Http
-import akka.http.scaladsl.model.ws.{BinaryMessage, Message, TextMessage, UpgradeToWebSocket, WebSocketUpgrade}
-import akka.http.scaladsl.model.{AttributeKeys, HttpRequest, HttpResponse}
+import akka.http.scaladsl.model.ws.{BinaryMessage, Message, TextMessage}
+import akka.http.scaladsl.model.{HttpRequest, HttpResponse}
 import akka.stream._
-import akka.stream.scaladsl.{Flow, Sink}
+import akka.stream.scaladsl.Flow
 
 
 object TestServer extends CrossScalaVersionAkkaApi {
@@ -25,7 +24,7 @@ object TestServer extends CrossScalaVersionAkkaApi {
 
     val requestHandler: HttpRequest => HttpResponse = {
       (req: HttpRequest) =>
-        req.attribute(AttributeKeys.webSocketUpgrade) match {
+        websocketAttribution(req) match {
           case Some(upgrade) => upgrade handleMessages service
           case None          => HttpResponse(400, entity = "Not a valid websocket request!")
         }