diff --git a/scripts/pnglibconf.mak b/scripts/pnglibconf.mak
index 883f93212..c125ca2c9 100755
--- a/scripts/pnglibconf.mak
+++ b/scripts/pnglibconf.mak
@@ -49,6 +49,7 @@ pnglibconf.dfn: $(srcdir)/scripts/pnglibconf.dfa $(srcdir)/scripts/options.awk $
 	$(MOVE) pnglibconf.tmp $@
 
 clean-pnglibconf:
-	$(DELETE) pnglibconf.h pnglibconf.c pnglibconf.out
+	$(DELETE) pnglibconf.h pnglibconf.c pnglibconf.out pnglibconf.pre \
+	pnglibconf.dfn
 
 clean: clean-pnglibconf