diff --git a/Makefile b/Makefile
index 6395f84..03ba9ac 100644
--- a/Makefile
+++ b/Makefile
@@ -47,7 +47,7 @@ VCS-PULLFLAGS =
 #
 LEG = ./peg/leg/leg
 %.leg.go: %.leg $(LEG)
-	$(LEG) $<
+	$(LEG) -switch $<
 
 $(LEG):
 	if(! test -d peg); then make peg; fi
diff --git a/parser.leg b/parser.leg
index bd80bb4..cd513ac 100644
--- a/parser.leg
+++ b/parser.leg
@@ -105,6 +105,7 @@ type Doc struct {
 
 %YYSTYPE *element
 
+%switchexcl(HtmlBlock Code Title RefTitle)
 
 Doc =       a:StartList ( Block { a = cons($$, a) } )*
             { p.tree = reverse(a) }