diff --git a/src/core/Akka.Streams.Tests/Dsl/QueueSourceSpec.cs b/src/core/Akka.Streams.Tests/Dsl/QueueSourceSpec.cs
index 644f0a7328b..decd764adc9 100644
--- a/src/core/Akka.Streams.Tests/Dsl/QueueSourceSpec.cs
+++ b/src/core/Akka.Streams.Tests/Dsl/QueueSourceSpec.cs
@@ -41,18 +41,20 @@ private static void AssertSuccess(Task<IQueueOfferResult> task)
         [Fact]
         public async Task QueueSource_should_emit_received_message_to_the_stream()
         {
-            var s = this.CreateManualSubscriberProbe<int>();
-            var queue =
-                Source.Queue<int>(10, OverflowStrategy.Fail).To(Sink.FromSubscriber(s)).Run(_materializer);
-            var sub = await s.ExpectSubscriptionAsync();
-
-            sub.Request(2);
-            AssertSuccess(queue.OfferAsync(1));
-            await s.ExpectNextAsync(1);
-            AssertSuccess(queue.OfferAsync(2));
-            await s.ExpectNextAsync(2);
-            AssertSuccess(queue.OfferAsync(3));
-            sub.Cancel();
+            await this.AssertAllStagesStoppedAsync(async () => {
+                var s = this.CreateManualSubscriberProbe<int>();
+                var queue =
+                    Source.Queue<int>(10, OverflowStrategy.Fail).To(Sink.FromSubscriber(s)).Run(_materializer);
+                var sub = await s.ExpectSubscriptionAsync();
+
+                sub.Request(2);
+                AssertSuccess(queue.OfferAsync(1));
+                await s.ExpectNextAsync(1);
+                AssertSuccess(queue.OfferAsync(2));
+                await s.ExpectNextAsync(2);
+                AssertSuccess(queue.OfferAsync(3));
+                sub.Cancel();
+            }, _materializer);
         }
 
         [Fact]
@@ -69,47 +71,53 @@ public void QueueSource_should_be_reusable()
         }
 
         [Fact]
-        public void QueueSource_should_reject_elements_when_backpressuring_with_maxBuffer_0()
+        public async Task QueueSource_should_reject_elements_when_backpressuring_with_maxBuffer_0()
         {
-            var t =
-                Source.Queue<int>(0, OverflowStrategy.Backpressure)
-                    .ToMaterialized(this.SinkProbe<int>(), Keep.Both)
-                    .Run(_materializer);
-            var source = t.Item1;
-            var probe = t.Item2;
-            var task = source.OfferAsync(42);
-            var ex = source.OfferAsync(43);
-            ex.Invoking(_ => _.Wait(TimeSpan.FromSeconds(3)))
-                .Should().Throw<IllegalStateException>()
-                .And.Message.Should()
-                .Contain("have to wait");
-
-            probe.RequestNext().Should().Be(42);
-            task.Wait(TimeSpan.FromSeconds(3)).Should().BeTrue();
-            task.Result.Should().Be(Enqueued.Instance);
-
+            await this.AssertAllStagesStoppedAsync(async () => {
+                var t =
+                    Source.Queue<int>(0, OverflowStrategy.Backpressure)
+                        .ToMaterialized(this.SinkProbe<int>(), Keep.Both)
+                        .Run(_materializer);
+                var source = t.Item1;
+                var probe = t.Item2;
+                var task = source.OfferAsync(42);
+                var ex = source.OfferAsync(43);
+                ex.Invoking(_ => _.Wait(TimeSpan.FromSeconds(3)))
+                    .Should().Throw<IllegalStateException>()
+                    .And.Message.Should()
+                    .Contain("have to wait");
+
+                await probe.RequestNextAsync(42);
+                task.Wait(TimeSpan.FromSeconds(3)).Should().BeTrue();
+                task.Result.Should().Be(Enqueued.Instance);
+
+                source.Complete();
+                await probe.ExpectCompleteAsync();
+            }, _materializer);
         }
 
         [Fact]
         public async Task QueueSource_should_buffer_when_needed()
         {
-            var s = this.CreateManualSubscriberProbe<int>();
-            var queue =
-                Source.Queue<int>(100, OverflowStrategy.DropHead)
-                    .To(Sink.FromSubscriber(s))
-                    .Run(_materializer);
-            var sub = await s.ExpectSubscriptionAsync();
-
-            for (var i = 1; i <= 20; i++) AssertSuccess(queue.OfferAsync(i));
-            sub.Request(10);
-            for (var i = 1; i <= 10; i++) AssertSuccess(queue.OfferAsync(i));
-            sub.Request(10);
-            for (var i = 11; i <= 20; i++) AssertSuccess(queue.OfferAsync(i));
-
-            for (var i = 200; i <= 399; i++) AssertSuccess(queue.OfferAsync(i));
-            sub.Request(100);
-            for (var i = 300; i <= 399; i++) AssertSuccess(queue.OfferAsync(i));
-            sub.Cancel();
+            await this.AssertAllStagesStoppedAsync(async () => {
+                var s = this.CreateManualSubscriberProbe<int>();
+                var queue =
+                    Source.Queue<int>(100, OverflowStrategy.DropHead)
+                        .To(Sink.FromSubscriber(s))
+                        .Run(_materializer);
+                var sub = await s.ExpectSubscriptionAsync();
+
+                for (var i = 1; i <= 20; i++) AssertSuccess(queue.OfferAsync(i));
+                sub.Request(10);
+                for (var i = 1; i <= 10; i++) AssertSuccess(queue.OfferAsync(i));
+                sub.Request(10);
+                for (var i = 11; i <= 20; i++) AssertSuccess(queue.OfferAsync(i));
+
+                for (var i = 200; i <= 399; i++) AssertSuccess(queue.OfferAsync(i));
+                sub.Request(100);
+                for (var i = 300; i <= 399; i++) AssertSuccess(queue.OfferAsync(i));
+                sub.Cancel();
+            }, _materializer);
         }
 
         [Fact]