diff --git a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/StreamConvertersSpec.scala b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/StreamConvertersSpec.scala
index 24a0be5102..72d0ccbcce 100644
--- a/akka-stream-tests/src/test/scala/akka/stream/scaladsl/StreamConvertersSpec.scala
+++ b/akka-stream-tests/src/test/scala/akka/stream/scaladsl/StreamConvertersSpec.scala
@@ -14,8 +14,11 @@ import java.util.stream.BaseStream
 import java.util.stream.Collector
 import java.util.stream.Collectors
 
+import akka.stream.ActorAttributes
 import akka.stream.testkit.StreamSpec
 import akka.stream.testkit.Utils.TE
+import akka.util.ByteString
+
 import akka.testkit.DefaultTimeout
 import org.scalatest.time.Millis
 import org.scalatest.time.Span
@@ -309,7 +312,33 @@ class StreamConvertersSpec extends StreamSpec with DefaultTimeout {
         Await.result(future, 300.millis)
       }
     }
-
   }
 
+  "InputStream Sink" must {
+    "produce a single value" in {
+      val source = Source.single(ByteString("ASDF"))
+      val sink =
+        StreamConverters.asInputStream().withAttributes(ActorAttributes.dispatcher("akka.test.stream-dispatcher"))
+
+      val is = source.runWith(sink)
+      is.read() should be('A')
+      val target = Array[Byte](0, 0, 0)
+      is.read(target, 1, 2)
+      target should be(Array[Byte](0, 'S', 'D'))
+      is.read() should be('F')
+      is.read() should be(-1)
+      is.close()
+    }
+    // As specified in the Closeable interface, #28664
+    "withstand being closed twice" in {
+      val source = Source.single(ByteString("ASDF"))
+      val sink =
+        StreamConverters.asInputStream().withAttributes(ActorAttributes.dispatcher("akka.test.stream-dispatcher"))
+
+      val is = source.runWith(sink)
+      is.read() should be('A')
+      is.close()
+      is.close()
+    }
+  }
 }
diff --git a/akka-stream/src/main/mima-filters/2.6.3.backwards.excludes/28681-allow-closing-inputstream-twice b/akka-stream/src/main/mima-filters/2.6.3.backwards.excludes/28681-allow-closing-inputstream-twice
new file mode 100644
index 0000000000..270658d410
--- /dev/null
+++ b/akka-stream/src/main/mima-filters/2.6.3.backwards.excludes/28681-allow-closing-inputstream-twice
@@ -0,0 +1,3 @@
+# private[stream]
+ProblemFilters.exclude[IncompatibleResultTypeProblem]("akka.stream.impl.io.InputStreamAdapter.isActive")
+ProblemFilters.exclude[DirectMissingMethodProblem]("akka.stream.impl.io.InputStreamAdapter.isActive_=")
diff --git a/akka-stream/src/main/scala/akka/stream/impl/io/InputStreamSinkStage.scala b/akka-stream/src/main/scala/akka/stream/impl/io/InputStreamSinkStage.scala
index b0f64a3acc..2651e45528 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/io/InputStreamSinkStage.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/io/InputStreamSinkStage.scala
@@ -6,6 +6,7 @@ package akka.stream.impl.io
 
 import java.io.{ IOException, InputStream }
 import java.util.concurrent.{ BlockingQueue, LinkedBlockingDeque, TimeUnit }
+import java.util.concurrent.atomic.AtomicBoolean
 
 import akka.annotation.InternalApi
 import akka.stream.Attributes.InputBuffer
@@ -118,14 +119,14 @@ private[stream] object InputStreamSinkStage {
     extends InputStream {
 
   var isInitialized = false
-  var isActive = true
+  val isActive = new AtomicBoolean(true)
   var isStageAlive = true
   def subscriberClosedException = new IOException("Reactive stream is terminated, no reads are possible")
   var detachedChunk: Option[ByteString] = None
 
   @scala.throws(classOf[IOException])
   private[this] def executeIfNotClosed[T](f: () => T): T =
-    if (isActive) {
+    if (isActive.get()) {
       waitIfNotInitialized()
       f()
     } else throw subscriberClosedException
@@ -187,11 +188,10 @@ private[stream] object InputStreamSinkStage {
 
   @scala.throws(classOf[IOException])
   override def close(): Unit = {
-    executeIfNotClosed(() => {
+    if (isActive.getAndSet(false)) {
       // at this point Subscriber may be already terminated
       if (isStageAlive) sendToStage(Close)
-      isActive = false
-    })
+    }
   }
 
   @tailrec