diff --git a/bison.jam b/bison.jam
index 4a7c2453e..c43811009 100644
--- a/bison.jam
+++ b/bison.jam
@@ -1,3 +1,7 @@
+#  Copyright (C) Vladimir Prus 2002. Permission to copy, use, modify, sell and
+#  distribute this software is granted provided this copyright notice appears in
+#  all copies. This software is provided "as is" without express or implied
+#  warranty, and with no claim as to its suitability for any purpose.
 
 import generators ;
 
@@ -10,7 +14,7 @@ rule bison ( dst dst_header : src : properties * )
     local r = [ property.select bison.prefix : $(properties) ] ;
     if $(r)
     {
-	PREFIX_OPT on $(<) = -p $(r:G=) ;
+        PREFIX_OPT on $(<) = -p $(r:G=) ;
     }
 }