diff --git a/docs/enhanced_proto.md b/docs/enhanced_proto.md
index 36ea9604..e16af1a7 100644
--- a/docs/enhanced_proto.md
+++ b/docs/enhanced_proto.md
@@ -31,6 +31,7 @@ first    second
  * arbitration start request  
    `<START> <master>`  
    Requests the start of the arbitration process after the next received `<SYN>` symbol with the specified master address in `d`.
+   If the master address is `<SYN>`, the current arbitration is supposed to be cancelled.
 
 #### from interface to ebusd
   * initialization response