src/Pure/Isar/isar_syn.ML

 val init_toplevelP =
   OuterSyntax.improper_command "init_toplevel" "restart Isar toplevel loop" K.control
     (Scan.succeed IsarCmd.init_toplevel);
 
 val welcomeP =
-  OuterSyntax.improper_command "welcome" "print welcome message" K.control
+  OuterSyntax.improper_command "welcome" "print welcome message" K.diag
     (Scan.succeed IsarCmd.welcome);
 
 
 
 (** the Pure outer syntax **)