diff --git a/src/proto/server/client.rs b/src/proto/server/client.rs
index 1e253b9..a01a485 100644
--- a/src/proto/server/client.rs
+++ b/src/proto/server/client.rs
@@ -42,10 +42,22 @@ pub enum ClientLoginError {
 /// An error that arose while running the client.
 #[derive(Debug, Error)]
 pub enum ClientRunError {
+  #[error("underlying stream was closed unexpectedly")]
+  StreamClosed,
+
   #[error("i/o error: {0}")]
   IOError(#[from] io::Error),
 }
 
+impl ClientRunError {
+  fn is_stream_closed(&self) -> bool {
+    match self {
+      ClientRunError::StreamClosed => true,
+      _ => false,
+    }
+  }
+}
+
 enum RunOnceResult {
   Break,
   Continue,
@@ -126,8 +138,7 @@ impl Client {
             debug!("Client: received response: {:?}", response);
             Ok(RunOnceResult::Response(response))
           }
-          // TODO: Consider returning error here.
-          None => Ok(RunOnceResult::Break),
+          None => Err(ClientRunError::StreamClosed),
         }
       },
     )
@@ -166,6 +177,7 @@ impl Client {
 mod tests {
   use futures::stream::{empty, StreamExt};
   use tokio::net;
+  use tokio::sync::mpsc;
 
   use crate::proto::server::testing::{fake_server, UserStatusMap};
   use crate::proto::server::{
@@ -256,4 +268,47 @@ mod tests {
     handle.shutdown();
     server_task.await.unwrap().unwrap();
   }
+
+  #[tokio::test]
+  async fn stream_closed() {
+    init();
+
+    let (server, handle) = fake_server().await.unwrap();
+    let server_task = tokio::spawn(server.serve());
+
+    let stream = net::TcpStream::connect(handle.address()).await.unwrap();
+
+    let user_name = "alice".to_string();
+    let password = "sekrit".to_string();
+    let credentials = Credentials::new(user_name, password).unwrap();
+
+    let options = ClientOptions {
+      credentials,
+      version: Version::default(),
+    };
+    let client = Client::login(stream, options).await.unwrap();
+
+    let (_request_tx, mut request_rx) = mpsc::channel(1);
+    let outbound = Box::pin(async_stream::stream! {
+      while let Some(request) = request_rx.recv().await {
+        yield request;
+      }
+    });
+
+    let mut inbound = client.run(outbound);
+
+    // Server shuts down, closing its connection before the client has had a
+    // chance to send all of `outbound`.
+    handle.shutdown();
+
+    // Check that the client returns the correct error.
+    assert!(inbound
+      .next()
+      .await
+      .unwrap()
+      .unwrap_err()
+      .is_stream_closed());
+
+    server_task.await.unwrap().unwrap();
+  }
 }