diff --git a/quinn-proto/src/endpoint.rs b/quinn-proto/src/endpoint.rs
index 75998b2d4c..f088ec27ab 100644
--- a/quinn-proto/src/endpoint.rs
+++ b/quinn-proto/src/endpoint.rs
@@ -653,6 +653,13 @@ impl Endpoint {
         }
     }
 
+    /// Rejects new connections without affecting existing connections.
+    pub fn reject_new_connections(&mut self) {
+        if let Some(config) = self.server_config.as_mut() {
+            Arc::make_mut(config).concurrent_connections(0);
+        }
+    }
+
     /// Access the configuration used by this endpoint
     pub fn config(&self) -> &EndpointConfig {
         &self.config
diff --git a/quinn-proto/src/tests/mod.rs b/quinn-proto/src/tests/mod.rs
index 449dd82e4c..42075da7de 100644
--- a/quinn-proto/src/tests/mod.rs
+++ b/quinn-proto/src/tests/mod.rs
@@ -2193,3 +2193,11 @@ fn stream_chunks(mut recv: RecvStream) -> Vec<u8> {
 
     buf
 }
+
+#[test]
+fn reject_new_connections() {
+    let _guard = subscribe();
+    let mut pair = Pair::default();
+    pair.server.reject_new_connections();
+    pair.assert_connection_refused();
+}
diff --git a/quinn-proto/src/tests/util.rs b/quinn-proto/src/tests/util.rs
index 97f306d18b..48bc953231 100644
--- a/quinn-proto/src/tests/util.rs
+++ b/quinn-proto/src/tests/util.rs
@@ -166,6 +166,16 @@ impl Pair {
         }
     }
 
+    /// Attempts to connect, asserting that the server doesn't accept the
+    /// connection and the client marks the connection as closed.
+    pub(super) fn assert_connection_refused(&mut self) {
+        dbg!(&self.client.connections);
+        let client_ch = self.begin_connect(client_config());
+        self.drive();
+        self.server.assert_no_accept();
+        assert!(self.client.connections.get(&client_ch).unwrap().is_closed());
+    }
+
     pub(super) fn connect(&mut self) -> (ConnectionHandle, ConnectionHandle) {
         self.connect_with(client_config())
     }
diff --git a/quinn/src/endpoint.rs b/quinn/src/endpoint.rs
index 03b9015951..5642047feb 100644
--- a/quinn/src/endpoint.rs
+++ b/quinn/src/endpoint.rs
@@ -236,6 +236,16 @@ impl Endpoint {
         self.inner.state.lock().unwrap().socket.local_addr()
     }
 
+    /// Rejects new connections without affecting existing connections.
+    pub fn reject_new_connections(&self) {
+        self.inner
+            .state
+            .lock()
+            .unwrap()
+            .inner
+            .reject_new_connections();
+    }
+
     /// Close all of this endpoint's connections immediately and cease accepting new connections.
     ///
     /// See [`Connection::close()`] for details.