diff --git a/dev/core/src/com/google/gwt/dev/shell/BrowserChannel.java b/dev/core/src/com/google/gwt/dev/shell/BrowserChannel.java
index be5c3b3..e905589 100644
--- a/dev/core/src/com/google/gwt/dev/shell/BrowserChannel.java
+++ b/dev/core/src/com/google/gwt/dev/shell/BrowserChannel.java
@@ -1386,6 +1386,7 @@
       stream.writeByte(MessageType.SWITCH_TRANSPORT.getId());
       writeUtf8String(stream, transport);
       writeUtf8String(stream, transportArgs);
+      stream.flush();
     }
   }