diff --git a/Capnp.Net.Runtime.Tests/Interception.cs b/Capnp.Net.Runtime.Tests/Interception.cs
index ab6b9f4..dee17a0 100644
--- a/Capnp.Net.Runtime.Tests/Interception.cs
+++ b/Capnp.Net.Runtime.Tests/Interception.cs
@@ -310,8 +310,8 @@ namespace Capnp.Net.Runtime.Tests
                     Assert.IsTrue(cc.CancelFromAlice.IsCancellationRequested);
 
                     cc.ForwardToBob();
-                    Assert.IsTrue(policy.Returns.ReceiveAsync().Wait(MediumNonDbgTimeout));
-                    Assert.IsTrue(cc.ReturnCanceled);
+                    Assert.IsTrue(policy.Returns.ReceiveAsync().Wait(MediumNonDbgTimeout), "must return");
+                    Assert.IsTrue(cc.ReturnCanceled, "must be canceled");
                     cc.ReturnCanceled = false;
                     cc.Exception = "Cancelled";
 
diff --git a/Capnp.Net.Runtime.Tests/Mock/TestCapImplementations.cs b/Capnp.Net.Runtime.Tests/Mock/TestCapImplementations.cs
index 5d19630..630d527 100644
--- a/Capnp.Net.Runtime.Tests/Mock/TestCapImplementations.cs
+++ b/Capnp.Net.Runtime.Tests/Mock/TestCapImplementations.cs
@@ -432,6 +432,7 @@ namespace Capnp.Net.Runtime.Tests.GenImpls
         public virtual Task<string> Foo(uint i, bool j, CancellationToken cancellationToken)
         {
             Interlocked.Increment(ref _counters.CallCount);
+            cancellationToken.ThrowIfCancellationRequested();
             Assert.AreEqual(123u, i);
             Assert.IsTrue(j);
             return Task.FromResult("foo");