diff --git a/akka-http-core/src/main/scala/akka/http/impl/engine/server/HttpServerBluePrint.scala b/akka-http-core/src/main/scala/akka/http/impl/engine/server/HttpServerBluePrint.scala
index 301d542369..80e8fda926 100644
--- a/akka-http-core/src/main/scala/akka/http/impl/engine/server/HttpServerBluePrint.scala
+++ b/akka-http-core/src/main/scala/akka/http/impl/engine/server/HttpServerBluePrint.scala
@@ -421,7 +421,7 @@ private[http] object HttpServerBluePrint {
 
           emit(responseCtxOut, ResponseRenderingContext(response, requestStart.method, requestStart.protocol, close),
             pullHttpResponseIn)
-          if (close && requestStart.expect100Continue) pull(requestParsingIn)
+          if (!isClosed(requestParsingIn) && close && requestStart.expect100Continue) pull(requestParsingIn)
         }
         override def onUpstreamFinish() =
           if (openRequests.isEmpty && isClosed(requestParsingIn)) completeStage()
diff --git a/akka-http-core/src/test/scala/akka/http/impl/engine/server/HttpServerBug2108Spec.scala b/akka-http-core/src/test/scala/akka/http/impl/engine/server/HttpServerBug2108Spec.scala
new file mode 100644
index 0000000000..9428ae00f7
--- /dev/null
+++ b/akka-http-core/src/test/scala/akka/http/impl/engine/server/HttpServerBug2108Spec.scala
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2009-2016 Lightbend Inc. <http://www.lightbend.com>
+ */
+package akka.http.impl.engine.server
+
+import akka.http.scaladsl.model.HttpEntity.Chunked
+import akka.http.scaladsl.model.HttpMethods._
+import akka.http.scaladsl.model.{ ContentType, HttpRequest, HttpResponse }
+import akka.http.scaladsl.model.MediaTypes._
+import akka.stream.{ ActorMaterializer, Materializer }
+import akka.stream.testkit.Utils.{ TE, _ }
+import akka.testkit.{ AkkaSpec, EventFilter }
+import org.scalatest.Inside
+
+import scala.concurrent.Await
+import scala.concurrent.duration._
+
+class HttpServerBug2108Spec extends AkkaSpec(
+  """
+   akka.loglevel = WARNING
+   akka.loggers = ["akka.testkit.TestEventListener", "akka.event.Logging$DefaultLogger"]
+   akka.http.server.request-timeout = infinite
+   akka.test.filter-leeway=300ms""") with Inside { spec ⇒
+  implicit val materializer = ActorMaterializer()
+
+  "The HttpServer" should {
+
+    "not cause internal graph failures when consuming a `100 Continue` entity triggers a failure" in assertAllStagesStopped(new HttpServerTestSetupBase {
+      override implicit def system = HttpServerBug2108Spec.this.system
+      override implicit def materializer: Materializer = HttpServerBug2108Spec.this.materializer
+
+      send("""POST / HTTP/1.1
+             |Host: example.com
+             |Expect: 100-continue
+             |Transfer-Encoding: chunked
+             |
+             |""")
+      inside(expectRequest()) {
+        case HttpRequest(POST, _, _, Chunked(ContentType(`application/octet-stream`, None), data), _) ⇒
+          val done = data.runForeach(_ ⇒ throw TE("failed on first chunk"))
+
+          expectResponseWithWipedDate(
+            """HTTP/1.1 100 Continue
+              |Server: akka-http/test
+              |Date: XXXX
+              |
+              |""")
+          send("""10
+                 |0123456789ABCDEF
+                 |0
+                 |
+                 |""")
+
+          // Bug #21008 does not actually ever make the request fail instead it logs the exception and behaves
+          // nicely so we need to check that the exception didn't get logged
+          var sawException = false
+          try {
+            EventFilter[IllegalArgumentException](occurrences = 1) intercept {
+              // make sure the failure has happened
+              Await.ready(done, 10.seconds)
+              // and then when the failure has happened/future completes, we push a reply
+              responses.sendNext(HttpResponse(entity = "Yeah"))
+
+            }
+            // got such an error, that is bad,
+            sawException = true
+          } catch {
+            case _: AssertionError ⇒ sawException = false
+          }
+          if (sawException) fail("HttpServerBluePrint.ControllerStage: requirement failed: Cannot pull closed port (requestParsingIn)")
+
+          // and the client should still get that ok
+          expectResponseWithWipedDate(
+            """HTTP/1.1 200 OK
+              |Server: akka-http/test
+              |Date: XXXX
+              |Connection: close
+              |Content-Type: text/plain; charset=UTF-8
+              |Content-Length: 4
+              |
+              |Yeah""")
+
+      }
+
+      netIn.sendComplete()
+      netOut.expectComplete()
+
+    })
+
+  }
+}