diff --git a/nix/modules/default/default.nix b/nix/modules/default/default.nix
index 1bd8f8d6..38468e44 100644
--- a/nix/modules/default/default.nix
+++ b/nix/modules/default/default.nix
@@ -40,18 +40,27 @@ in
             '';
             default = false;
           };
-          database.path = lib.mkOption {
-            type = types.nonEmptyStr;
-            readOnly = true;
-            description = ''
-              The path to store database files in.
+          database = {
+            backend = lib.mkOption {
+              type = types.nonEmptyStr;
+              description = ''
+                The database backend to use.
+              '';
+              default = "rocksdb";
+            };
+            path = lib.mkOption {
+              type = types.nonEmptyStr;
+              readOnly = true;
+              description = ''
+                The path to store database files in.
 
-              Note that this is read-only because this module makes use of
-              systemd's `StateDirectory` option.
-            '';
-            default = if cfg.settings.conduit_compat
-              then "/var/lib/matrix-conduit/database"
-              else "/var/lib/grapevine/database";
+                Note that this is read-only because this module makes use of
+                systemd's `StateDirectory` option.
+              '';
+              default = if cfg.settings.conduit_compat
+                then "/var/lib/matrix-conduit/database"
+                else "/var/lib/grapevine/database";
+            };
           };
           media.backend = {
             type = lib.mkOption {