diff --git a/configure.in b/configure.in
index 3b2b2e7f08..14451d8d12 100644
--- a/configure.in
+++ b/configure.in
@@ -83,7 +83,7 @@ dnl SLAPD Backend options
 OL_ARG_ENABLE(bdb2,[    --enable-bdb2	enable bdb2 backend], no)dnl
 OL_ARG_ENABLE(ldbm,[    --enable-ldbm	enable ldbm backend], yes)dnl
 OL_ARG_WITH(ldbm_api,[      --with-ldbm-api	use LDBM API], auto,
-	[auto db2 db gdbm ndbm manual])
+	[auto db2 db mdbm gdbm ndbm manual])
 OL_ARG_WITH(ldbm_type,[      --with-ldbm-type	use LDBM type], auto,
 	[auto btree hash])