diff --git a/include/ircd/fs/map.h b/include/ircd/fs/map.h
index 649f9981d..9b06a6fd6 100644
--- a/include/ircd/fs/map.h
+++ b/include/ircd/fs/map.h
@@ -29,8 +29,10 @@ struct ircd::fs::map
 {
 	struct opts;
 
+	static const opts default_opts;
+
 	map() = default;
-	map(const fd &, const opts &opts, const size_t &size = 0UL);
+	map(const fd &, const opts &opts = default_opts, const size_t &size = 0UL);
 	map(map &&) noexcept;
 	map(const map &) = delete;
 	map &operator=(map &&) noexcept;
diff --git a/ircd/fs.cc b/ircd/fs.cc
index 5a19536b0..78d46dab4 100644
--- a/ircd/fs.cc
+++ b/ircd/fs.cc
@@ -2049,6 +2049,9 @@ ircd::fs::advise(const map &map,
 // map::map
 //
 
+decltype(ircd::fs::map::default_opts)
+ircd::fs::map::default_opts;
+
 ircd::fs::map::map(const fd &fd,
                    const opts &opts,
                    const size_t &size)