diff --git a/src/main/java/net/schmizz/sshj/transport/TransportImpl.java b/src/main/java/net/schmizz/sshj/transport/TransportImpl.java
index 7e717103..289a4430 100644
--- a/src/main/java/net/schmizz/sshj/transport/TransportImpl.java
+++ b/src/main/java/net/schmizz/sshj/transport/TransportImpl.java
@@ -151,6 +151,7 @@ public final class TransportImpl
 
             log.info("Client identity string: {}", clientID);
             connInfo.out.write((clientID + "\r\n").getBytes(IOUtils.UTF8));
+            connInfo.out.flush();
 
             // Read server's ID
             final Buffer.PlainBuffer buf = new Buffer.PlainBuffer();