diff --git a/packages/cultnet-rs/src/rudp/send_failure_tests.rs b/packages/cultnet-rs/src/rudp/send_failure_tests.rs
index 49a80f80..4e5b7125 100644
--- a/packages/cultnet-rs/src/rudp/send_failure_tests.rs
+++ b/packages/cultnet-rs/src/rudp/send_failure_tests.rs
@@ -414,3 +414,25 @@ fn a_peer_ended_in_the_resend_loop_is_sent_nothing_more_from_it() {
     assert_eq!(hub.stats().send_failures, 3);
     assert_eq!(hub.sessions().len(), 1);
 }
+
+#[test]
+fn a_refused_send_withdraws_the_fragments_the_window_queued_as_well() {
+    let (mut hub, _peer, session) = one_peer(Some(1));
+    let outstanding = hub.peers[&session.remote_addr]
+        .session
+        .outstanding_reliable_packet_count();
+    hub.unsendable_after.insert(session.remote_addr, 0);
+
+    // 1,100 one-byte fragments: the flow window admits the first ones and
+    // queues the rest, and the first datagram can never be sent.
+    hub.send(&session, "schema", vec![7; 1_100])
+        .expect_err("the first fragment can never be sent");
+
+    assert_eq!(
+        hub.peers[&session.remote_addr]
+            .session
+            .outstanding_reliable_packet_count(),
+        outstanding,
+        "nothing of the refused send stays queued"
+    );
+}
diff --git a/tests/GameCult.Networking.Tests/CultNetRudpSendFailureTests.cs b/tests/GameCult.Networking.Tests/CultNetRudpSendFailureTests.cs
index e79b319c..a3976375 100644
--- a/tests/GameCult.Networking.Tests/CultNetRudpSendFailureTests.cs
+++ b/tests/GameCult.Networking.Tests/CultNetRudpSendFailureTests.cs
@@ -176,6 +176,23 @@ namespace GameCult.Networking.Tests
             }
         }
 
+        [Test]
+        public void ARefusedSendWithdrawsTheFragmentsTheWindowQueuedAsWell()
+        {
+            var (server, _, x, _) = TwoPeers(maxFragmentBytes: 1);
+            using (server)
+            {
+                var outstanding = x.Server.Session.OutstandingReliablePacketCount;
+                server.UnsendableAfter[x.EndPoint] = 0;
+
+                // 1,100 one-byte fragments: the flow window admits the first ones and queues the rest,
+                // and the first datagram can never be sent.
+                Assert.Throws<SocketException>(() => server.SendSchema(x.Server, new byte[1_100]));
+
+                Assert.That(x.Server.Session.OutstandingReliablePacketCount, Is.EqualTo(outstanding), "nothing of the refused send stays queued");
+            }
+        }
+
         [Test]
         public void ASendThatFailsPermanentlyAfterAFragmentLeftEndsTheSession()
         {