diff --git a/global/fs/zfs.nix b/global/fs/zfs.nix
index 66252da3..149273c5 100644
--- a/global/fs/zfs.nix
+++ b/global/fs/zfs.nix
@@ -20,6 +20,7 @@ in {
       type = with types; attrsOf str;
       description = "zfs dataset mountpoints";
     };
+    externalStore = mkEnableOption "external nix store filesystem";
   };
 
   config = mkIf (cfg.type == "zfs") {
@@ -29,10 +30,11 @@ in {
       # required by impermanence
       neededForBoot = true;
     }) cfg.zfs.mountpoints) // {
-      "/nix" =
+      "/nix" = (if !cfg.zfs.externalStore then
         { device = "${cfg.store}/nix";
           fsType = "zfs";
-        };
+        } else
+        { inherit (cfg.external) device fsType options; });
     };
     global.fs.zfs.mountpoints."/nix/persist" = "persist";