diff --git a/libtorrent/configure.ac b/libtorrent/configure.ac
index 5ac6e194..c3480fe3 100644
--- a/libtorrent/configure.ac
+++ b/libtorrent/configure.ac
@@ -55,6 +55,7 @@ TORRENT_WITH_ADDRESS_SPACE
 TORRENT_WITHOUT_STATVFS
 TORRENT_WITHOUT_STATFS
 TORRENT_WITH_INOTIFY
+TORRENT_WITH_UDNS
 
 CC_ATTRIBUTE_VISIBILITY