diff --git a/doc/Makefile.in b/doc/Makefile.in
index 96dd7af7..ad95e8ae 100644
--- a/doc/Makefile.in
+++ b/doc/Makefile.in
@@ -18,7 +18,8 @@ DISTDIR?=$(top_builddir)/@PACKAGE_TARNAME@-@PACKAGE_VERSION@
 FILES:=Makefile.in Doxyfile.in html
 
 doc:	Doxyfile
-	$(DOXYGEN) -l
+	@$(DOXYGEN) -u $< > /dev/null 2>&1
+	@$(DOXYGEN) -l
 	$(DOXYGEN) $< >./doxygen.out
 
 clean: