diff --git a/lib/src/ssh_transport.dart b/lib/src/ssh_transport.dart
index 46ba5e4..2e6f61c 100644
--- a/lib/src/ssh_transport.dart
+++ b/lib/src/ssh_transport.dart
@@ -373,7 +373,7 @@ class SSHTransport {
     }
 
     final versionString = bufferString.substring(0, index);
-    if (!versionString.startsWith('SSH-2.0-')) {
+    if (!(versionString.startsWith('SSH-2.0-') || versionString.startsWith('SSH-1.99-'))) {
       socket.sink.add(latin1.encode('Protocol mismatch\r\n'));
       throw SSHHandshakeError('Invalid version: $versionString');
     }