diff --git a/akka-docs-dev/rst/java/code/docs/http/javadsl/server/WebsocketRoutingExample.java b/akka-docs-dev/rst/java/code/docs/http/javadsl/server/WebsocketRoutingExample.java
index e16219628d..343168491a 100644
--- a/akka-docs-dev/rst/java/code/docs/http/javadsl/server/WebsocketRoutingExample.java
+++ b/akka-docs-dev/rst/java/code/docs/http/javadsl/server/WebsocketRoutingExample.java
@@ -31,9 +31,9 @@ public class WebsocketRoutingExample extends HttpApp {
      * A handler that treats incoming messages as a name,
      * and responds with a greeting to that name
      */
-    public static Flow<Message, Message, Object> greeter() {
+    public static Flow<Message, Message, ?> greeter() {
         return
-            upcastMaterializerToObject(Flow.<Message>create())
+            Flow.<Message>create()
                 .collect(new JavaPartialFunction<Message, Message>() {
                     @Override
                     public Message apply(Message msg, boolean isCheck) throws Exception {
@@ -51,10 +51,4 @@ public class WebsocketRoutingExample extends HttpApp {
         else // ... this would suffice to handle all text messages in a streaming fashion
             return TextMessage.create(Source.single("Hello ").concat(msg.getStreamedText()));
     }
-
-    // needed because of #18028, see https://github.com/akka/akka/issues/18028
-    @SuppressWarnings("unchecked")
-    public static <T, U> Flow<T, U, Object> upcastMaterializerToObject(Flow< T, U, ?> flow) {
-        return (Flow<T, U, Object>) flow;
-    }
 }
diff --git a/akka-http-core/src/main/scala/akka/http/javadsl/model/ws/Websocket.scala b/akka-http-core/src/main/scala/akka/http/javadsl/model/ws/Websocket.scala
index 69b35faf63..31bdf1dc44 100644
--- a/akka-http-core/src/main/scala/akka/http/javadsl/model/ws/Websocket.scala
+++ b/akka-http-core/src/main/scala/akka/http/javadsl/model/ws/Websocket.scala
@@ -4,7 +4,6 @@
 
 package akka.http.javadsl.model.ws
 
-import akka.stream.Materializer
 import akka.stream.javadsl.Flow
 import akka.http.javadsl.model._
 import akka.http.impl.util.JavaMapping.Implicits._
diff --git a/akka-http/src/main/scala/akka/http/javadsl/server/directives/WebsocketDirectives.scala b/akka-http/src/main/scala/akka/http/javadsl/server/directives/WebsocketDirectives.scala
index 763991cf4e..12d42c4ba9 100644
--- a/akka-http/src/main/scala/akka/http/javadsl/server/directives/WebsocketDirectives.scala
+++ b/akka-http/src/main/scala/akka/http/javadsl/server/directives/WebsocketDirectives.scala
@@ -14,6 +14,6 @@ abstract class WebsocketDirectives extends SchemeDirectives {
    * Handles websocket requests with the given handler and rejects other requests with a
    * [[ExpectedWebsocketRequestRejection]].
    */
-  def handleWebsocketMessages(handler: Flow[Message, Message, Any]): Route =
+  def handleWebsocketMessages(handler: Flow[Message, Message, _]): Route =
     RouteStructure.HandleWebsocketMessages(handler)
 }