diff --git a/PROTOCOL.u2f b/PROTOCOL.u2f
index 4bd166bbb..8ccd20b56 100644
--- a/PROTOCOL.u2f
+++ b/PROTOCOL.u2f
@@ -68,8 +68,8 @@ The corresponding private key contains:
 	string		curve name
 	ec_point	Q
 	string		application (user-specified, but typically "ssh:")
+	uint8		flags
 	string		key_handle
-	uint32		flags
 	string		reserved
 
 The certificate form of a SSH U2F key appends the usual certificate