diff --git a/akka-http-core/src/main/scala/akka/http/engine/ws/Websocket.scala b/akka-http-core/src/main/scala/akka/http/engine/ws/Websocket.scala
index e19827d0d1..fdf758a27b 100644
--- a/akka-http-core/src/main/scala/akka/http/engine/ws/Websocket.scala
+++ b/akka-http-core/src/main/scala/akka/http/engine/ws/Websocket.scala
@@ -28,13 +28,18 @@ private[http] object Websocket {
                         closeTimeout: FiniteDuration = 3.seconds): Flow[FrameEvent, FrameEvent, Unit] = {
     /** Completes this branch of the flow if no more messages are expected and converts close codes into errors */
     class PrepareForUserHandler extends PushStage[MessagePart, MessagePart] {
+      var inMessage = false
       def onPush(elem: MessagePart, ctx: Context[MessagePart]): SyncDirective = elem match {
         case PeerClosed(code, reason) ⇒
           if (code.exists(Protocol.CloseCodes.isError)) ctx.fail(new ProtocolException(s"Peer closed connection with code $code"))
+          else if (inMessage) ctx.fail(new ProtocolException(s"Truncated message, peer closed connection in the middle of message."))
           else ctx.finish()
         case ActivelyCloseWithCode(code, reason) ⇒
           if (code.exists(Protocol.CloseCodes.isError)) ctx.fail(new ProtocolException(s"Closing connection with error code $code"))
-          else ctx.finish()
+          else ctx.fail(new IllegalStateException("Regular close from FrameHandler is unexpected"))
+        case x: MessageDataPart ⇒
+          inMessage = !x.last
+          ctx.push(x)
         case x ⇒ ctx.push(x)
       }
     }
diff --git a/akka-http-core/src/test/scala/akka/http/engine/ws/MessageSpec.scala b/akka-http-core/src/test/scala/akka/http/engine/ws/MessageSpec.scala
index c47ec4d5d9..bfd054f73a 100644
--- a/akka-http-core/src/test/scala/akka/http/engine/ws/MessageSpec.scala
+++ b/akka-http-core/src/test/scala/akka/http/engine/ws/MessageSpec.scala
@@ -477,8 +477,7 @@ class MessageSpec extends FreeSpec with Matchers with WithMaterializerSpec {
         expectCloseCodeOnNetwork(Protocol.CloseCodes.Regular)
         netOut.expectComplete()
       }
-      "after receiving regular close frame when fragmented message is still open" in pendingUntilFixed {
-        pending
+      "after receiving regular close frame when fragmented message is still open" in {
         new ServerTestSetup {
           netOutSub.request(10)
           messageInSub.request(10)
@@ -496,7 +495,11 @@ class MessageSpec extends FreeSpec with Matchers with WithMaterializerSpec {
           inSubscriber.expectNext(outData)
 
           pushInput(closeFrame(Protocol.CloseCodes.Regular, mask = true))
-          messageIn.expectComplete()
+
+          // This is arguable: we could also just fail the subStream but complete the main message stream regularly.
+          // However, truncating an ongoing message by closing without sending a `Continuation(fin = true)` first
+          // could be seen as something being amiss.
+          messageIn.expectError()
           inSubscriber.expectError()
           // truncation of open message