diff --git a/src/wsproto/handshake.py b/src/wsproto/handshake.py
index 72af722..a79bf07 100644
--- a/src/wsproto/handshake.py
+++ b/src/wsproto/handshake.py
@@ -286,7 +286,7 @@ def _accept(self, event: AcceptConnection) -> bytes:
                 headers.append((b"Sec-WebSocket-Extensions", accepts))
 
         response = h11.InformationalResponse(
-            status_code=101, headers=headers + event.extra_headers
+            status_code=101, headers=headers + event.extra_headers, reason=b"Switching Protocols"
         )
         self._connection = Connection(
             ConnectionType.CLIENT if self.client else ConnectionType.SERVER,