diff --git a/doc/Makefile.am b/doc/Makefile.am
index 401c1b3..a66420c 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -218,6 +218,9 @@
 	@true
 else
 htmldoc_DATA += $(srcdir)/$(HTML_DIR)/*
+.fncs.sgml:
+	$(AM_V_GEN) $(RM) $@; \
+	touch -r $< $@
 all-local:
 clean-local:
 dist-local-check-docs-enabled: