diff --git a/Makefile.am b/Makefile.am
index 42561382..0a4a1048 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -31,5 +31,5 @@ EXTRA_DIST = bison.1 bison.s1 bison.hairy REFERENCES configure.bat	\
 
 bison.simple: bison.s1 Makefile
 	-rm -f $@
-	sed -e "/^#line/ s|bison|$(datadir)/bison|" -e "s/@bison_version@/$(VERSION)/" < $< > $@-tmp
+	sed -e "/^#line/ s|bison|$(datadir)/bison|" -e "s/@bison_version@/$(VERSION)/" < $(srcdir)/bison.s1 > $@-tmp
 	mv $@-tmp $@