diff --git a/jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/api/Stream.java b/jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/api/Stream.java
index b7628584561..1727eaec4e1 100644
--- a/jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/api/Stream.java
+++ b/jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/api/Stream.java
@@ -87,6 +87,14 @@ public interface Stream
      * <p>{@link Stream.Data} objects may be stored away for later, asynchronous,
      * processing (for example, to process them only when all of them have been
      * received).</p>
+     * <p>This method <em>must only</em> be called when there is no outstanding
+     * {@link #demand() demand}.</p>
+     * <p>Practically, this means that this method should be called either
+     * synchronously from within {@link Stream.Listener#onDataAvailable(Stream)},
+     * or applications must arrange, for example using a
+     * {@link java.util.concurrent.Semaphore}, that a call to
+     * {@link Stream.Listener#onDataAvailable(Stream)} is made before
+     * calling this method (possibly from a different thread).</p>
      *
      * @return a {@link Stream.Data} object containing the request bytes or
      * the response bytes, or null if no bytes are available
diff --git a/jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/internal/HTTP3StreamConnection.java b/jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/internal/HTTP3StreamConnection.java
index 0e5a55feefd..02e76200c39 100644
--- a/jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/internal/HTTP3StreamConnection.java
+++ b/jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/internal/HTTP3StreamConnection.java
@@ -131,6 +131,9 @@ public abstract class HTTP3StreamConnection extends AbstractConnection
         if (LOG.isDebugEnabled())
             LOG.debug("reading data on {}", this);
 
+        if (hasDemand())
+            throw new IllegalStateException("invalid call to readData(): outstanding demand");
+
         switch (parseAndFill())
         {
             case FRAME:
diff --git a/jetty-http3/http3-tests/src/test/java/org/eclipse/jetty/http3/tests/HTTP3DataDemandTest.java b/jetty-http3/http3-tests/src/test/java/org/eclipse/jetty/http3/tests/HTTP3DataDemandTest.java
index 9e5f9680e04..691345f75ef 100644
--- a/jetty-http3/http3-tests/src/test/java/org/eclipse/jetty/http3/tests/HTTP3DataDemandTest.java
+++ b/jetty-http3/http3-tests/src/test/java/org/eclipse/jetty/http3/tests/HTTP3DataDemandTest.java
@@ -19,6 +19,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Random;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Semaphore;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
@@ -465,4 +466,84 @@ public class HTTP3DataDemandTest extends AbstractHTTP3ClientServerTest
 
         assertTrue(serverDataLatch.await(5, TimeUnit.SECONDS));
     }
+
+    @Test
+    public void testBlockingReadInADifferentThread() throws Exception
+    {
+        CountDownLatch blockLatch = new CountDownLatch(1);
+        CountDownLatch dataLatch = new CountDownLatch(1);
+        startServer(new Session.Server.Listener()
+        {
+            @Override
+            public Stream.Listener onRequest(Stream stream, HeadersFrame frame)
+            {
+                stream.demand();
+
+                // Simulate a thread dispatched to read the request content with blocking I/O.
+                Semaphore semaphore = new Semaphore(0);
+                new Thread(() ->
+                {
+                    try
+                    {
+                        // Wait for onDataAvailable() to be called before start reading.
+                        semaphore.acquire();
+                        while (true)
+                        {
+                            Stream.Data data = stream.readData();
+                            if (data != null)
+                            {
+                                // Consume the data.
+                                data.complete();
+                                if (data.isLast())
+                                {
+                                    dataLatch.countDown();
+                                    return;
+                                }
+                            }
+                            else
+                            {
+                                // Demand and block.
+                                stream.demand();
+                                blockLatch.countDown();
+                                semaphore.acquire();
+                            }
+                        }
+                    }
+                    catch (InterruptedException x)
+                    {
+                        x.printStackTrace();
+                    }
+                }).start();
+
+                return new Stream.Listener()
+                {
+                    @Override
+                    public void onDataAvailable(Stream stream)
+                    {
+                        semaphore.release();
+                    }
+                };
+            }
+        });
+        startClient();
+
+        Session.Client session = client.connect(new InetSocketAddress("localhost", connector.getLocalPort()), new Session.Client.Listener() {})
+            .get(5, TimeUnit.SECONDS);
+
+        HttpURI uri = HttpURI.from("https://localhost:" + connector.getLocalPort() + "/");
+        MetaData.Request metaData = new MetaData.Request(HttpMethod.GET.asString(), uri, HttpVersion.HTTP_3, HttpFields.EMPTY);
+        HeadersFrame request = new HeadersFrame(metaData, false);
+        Stream stream = session.newRequest(request, new Stream.Listener() {}).get(5, TimeUnit.SECONDS);
+
+        // Send a first chunk of data.
+        stream.data(new DataFrame(ByteBuffer.allocate(16 * 1024), false));
+
+        // Wait some time until the server reads no data after the first chunk.
+        assertTrue(blockLatch.await(5, TimeUnit.SECONDS));
+
+        // Send the last chunk of data.
+        stream.data(new DataFrame(ByteBuffer.allocate(32 * 1024), true));
+
+        assertTrue(dataLatch.await(5, TimeUnit.SECONDS));
+    }
 }