diff --git a/akka-http-tests/src/test/java/akka/http/javadsl/server/CompleteTest.java b/akka-http-tests/src/test/java/akka/http/javadsl/server/CompleteTest.java
index 62d3d3e136f..6acd8614678 100644
--- a/akka-http-tests/src/test/java/akka/http/javadsl/server/CompleteTest.java
+++ b/akka-http-tests/src/test/java/akka/http/javadsl/server/CompleteTest.java
@@ -9,6 +9,7 @@
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionStage;
 
+import akka.http.javadsl.model.StatusCodes;
 import org.junit.Test;
 
 import akka.http.javadsl.marshallers.jackson.Jackson;
@@ -70,4 +71,64 @@ public void completeWithFuture() {
             .assertStatusCode(200)
             .assertEntity("42 + 23 = 65");
     }
+
+
+    private ExceptionHandler customExceptionHandler() {
+        return ExceptionHandler.newBuilder()
+                .match(IllegalStateException.class, ex ->
+                        complete(StatusCodes.SERVICE_UNAVAILABLE, "Custom Error"))
+                .build();
+    }
+
+    private void checkRoute(Route route) {
+        Route sealedRoute = route.seal(RejectionHandler.defaultHandler(), customExceptionHandler());
+        runRoute(sealedRoute, HttpRequest.GET("/crash"))
+                .assertStatusCode(StatusCodes.SERVICE_UNAVAILABLE)
+                .assertEntity("Custom Error");
+    }
+
+    @Test
+    public void completeOKWithFutureStringFailing() {
+        Route route = path("crash", () ->
+                completeOKWithFutureString(CompletableFuture.supplyAsync(() -> {
+                    throw new IllegalStateException("Boom!");
+                })));
+        checkRoute(route);
+    }
+
+    @Test
+    public void completeWithFutureStatusFailing() {
+        Route route = path("crash", () ->
+                completeWithFutureStatus(CompletableFuture.supplyAsync(() -> {
+                    throw new IllegalStateException("Boom!");
+                })));
+        checkRoute(route);
+    }
+
+    @Test
+    public void completeWithFutureFailing() {
+        Route route = path("crash", () ->
+                completeWithFuture(CompletableFuture.supplyAsync(() -> {
+                    throw new IllegalStateException("Boom!");
+                })));
+        checkRoute(route);
+    }
+
+    @Test
+    public void completeOKWithFutureFailing() {
+        Route route = path("crash", () ->
+                completeOKWithFuture(CompletableFuture.supplyAsync(() -> {
+                    throw new IllegalStateException("Boom!");
+                })));
+        checkRoute(route);
+    }
+
+    @Test
+    public void completeOKWithFutureTFailing() {
+        Route route = path("crash", () ->
+                completeOKWithFuture(CompletableFuture.<Integer>supplyAsync(() -> {
+                    throw new IllegalStateException("Boom!");
+                }), Jackson.marshaller()));
+        checkRoute(route);
+    }
 }
diff --git a/akka-http/src/main/scala/akka/http/javadsl/server/directives/RouteDirectives.scala b/akka-http/src/main/scala/akka/http/javadsl/server/directives/RouteDirectives.scala
index ee5a8765deb..dbcce3066c5 100644
--- a/akka-http/src/main/scala/akka/http/javadsl/server/directives/RouteDirectives.scala
+++ b/akka-http/src/main/scala/akka/http/javadsl/server/directives/RouteDirectives.scala
@@ -4,7 +4,7 @@
 
 package akka.http.javadsl.server.directives
 
-import java.util.concurrent.CompletionStage
+import java.util.concurrent.{ CompletionException, CompletionStage }
 
 import akka.dispatch.ExecutionContexts
 import akka.http.javadsl.marshalling.Marshaller
@@ -20,7 +20,7 @@ import akka.http.javadsl.model.RequestEntity
 import akka.http.javadsl.model.ResponseEntity
 import akka.http.javadsl.model.StatusCode
 import akka.http.javadsl.model.Uri
-import akka.http.javadsl.server.{ RoutingJavaMapping, Rejection, Route }
+import akka.http.javadsl.server.{ Rejection, Route, RoutingJavaMapping }
 import akka.http.scaladsl
 import akka.http.scaladsl.marshalling.Marshaller._
 import akka.http.scaladsl.marshalling.ToResponseMarshallable
@@ -239,7 +239,7 @@ abstract class RouteDirectives extends RespondWithDirectives {
    */
   @CorrespondsTo("complete")
   def completeWithFuture(value: CompletionStage[HttpResponse]) = RouteAdapter {
-    D.complete(value.asScala.fast.map(_.asScala))
+    D.complete(value.asScala.fast.map(_.asScala).recover(unwrapCompletionException))
   }
 
   /**
@@ -247,7 +247,7 @@ abstract class RouteDirectives extends RespondWithDirectives {
    */
   @CorrespondsTo("complete")
   def completeOKWithFuture(value: CompletionStage[RequestEntity]) = RouteAdapter {
-    D.complete(value.asScala.fast.map(_.asScala))
+    D.complete(value.asScala.fast.map(_.asScala).recover(unwrapCompletionException))
   }
 
   /**
@@ -255,7 +255,7 @@ abstract class RouteDirectives extends RespondWithDirectives {
    */
   @CorrespondsTo("complete")
   def completeOKWithFutureString(value: CompletionStage[String]) = RouteAdapter {
-    D.complete(value.asScala)
+    D.complete(value.asScala.recover(unwrapCompletionException))
   }
 
   /**
@@ -263,7 +263,7 @@ abstract class RouteDirectives extends RespondWithDirectives {
    */
   @CorrespondsTo("complete")
   def completeWithFutureStatus(status: CompletionStage[StatusCode]): Route = RouteAdapter {
-    D.complete(status.asScala.fast.map(_.asScala))
+    D.complete(status.asScala.fast.map(_.asScala).recover(unwrapCompletionException))
   }
 
   /**
@@ -271,7 +271,7 @@ abstract class RouteDirectives extends RespondWithDirectives {
    */
   @CorrespondsTo("complete")
   def completeOKWithFuture[T](value: CompletionStage[T], marshaller: Marshaller[T, RequestEntity]) = RouteAdapter {
-    D.complete(value.asScala.fast.map(v ⇒ ToResponseMarshallable(v)(fromToEntityMarshaller()(marshaller))))
+    D.complete(value.asScala.fast.map(v ⇒ ToResponseMarshallable(v)(fromToEntityMarshaller()(marshaller))).recover(unwrapCompletionException))
   }
 
   /**
@@ -279,7 +279,16 @@ abstract class RouteDirectives extends RespondWithDirectives {
    */
   @CorrespondsTo("complete")
   def completeWithFuture[T](value: CompletionStage[T], marshaller: Marshaller[T, HttpResponse]) = RouteAdapter {
-    D.complete(value.asScala.fast.map(v ⇒ ToResponseMarshallable(v)(marshaller)))
+    D.complete(value.asScala.fast.map(v ⇒ ToResponseMarshallable(v)(marshaller)).recover(unwrapCompletionException))
+  }
+
+  // TODO: This might need to be raised as an issue to scala-java8-compat instead.
+  // Right now, having this in Java:
+  //     CompletableFuture.supplyAsync(() -> { throw new IllegalArgumentException("always failing"); })
+  // will in fact fail the future with CompletionException.
+  private def unwrapCompletionException[T]: PartialFunction[Throwable, T] = {
+    case x: CompletionException if x.getCause ne null ⇒
+      throw x.getCause
   }
 
 }