diff --git a/nix/checks/configuration-test.nix b/nix/checks/configuration-test.nix
index a95edb83..c78f9b33 100644
--- a/nix/checks/configuration-test.nix
+++ b/nix/checks/configuration-test.nix
@@ -58,6 +58,16 @@ in
       }
     ];
     inherit full-text-search;
+    extraConfig = {
+      files = {
+        default-store = "database";
+        stores = {
+          minio = {
+            enabled = true;
+          };
+        };
+      };
+    };
   };
 
   environment.systemPackages =
diff --git a/nix/modules/joex.nix b/nix/modules/joex.nix
index e6d5dcce..72996727 100644
--- a/nix/modules/joex.nix
+++ b/nix/modules/joex.nix
@@ -3,10 +3,12 @@ overlay: { config, lib, pkgs, ... }:
 with lib;
 let
   cfg = config.services.docspell-joex;
+  # Extract the config without the extraConfig attribute. It will be merged later
+  declared_config = attrsets.filterAttrs (n: v: n != "extraConfig") cfg;
   user = if cfg.runAs == null then "docspell" else cfg.runAs;
   configFile = pkgs.writeText "docspell-joex.conf" ''
     {"docspell": { "joex":
-         ${builtins.toJSON cfg}
+      ${builtins.toJSON (lib.recursiveUpdate declared_config cfg.extraConfig)}
     }}
   '';
   defaults = {
@@ -1670,6 +1672,23 @@ in
         default = defaults.addons;
         description = "Addon executor config";
       };
+      extraConfig = mkOption {
+        type = types.attrs;
+        description = "Extra configuration for docspell server. Overwrites values in case of a conflict.";
+        default = { };
+        example = ''
+          {
+            files = {
+              default-store = "minio";
+              stores = {
+                minio = {
+                  enabled = true;
+                };
+              };
+            };
+          }
+        '';
+      };
     };
   };
 
diff --git a/nix/modules/server.nix b/nix/modules/server.nix
index 33e3aaa7..4a98c8dc 100644
--- a/nix/modules/server.nix
+++ b/nix/modules/server.nix
@@ -3,10 +3,12 @@ overlay: { config, lib, pkgs, ... }:
 with lib;
 let
   cfg = config.services.docspell-restserver;
+  # Extract the config without the extraConfig attribute. It will be merged later
+  declared_config = attrsets.filterAttrs (n: v: n != "extraConfig") cfg;
   user = if cfg.runAs == null then "docspell" else cfg.runAs;
   configFile = pkgs.writeText "docspell-server.conf" ''
     {"docspell": {"server":
-      ${builtins.toJSON cfg}
+      ${builtins.toJSON (lib.recursiveUpdate declared_config cfg.extraConfig)}
     }}
   '';
   defaults = {
@@ -839,6 +841,23 @@ in
         default = defaults.backend;
         description = "Configuration for the backend";
       };
+      extraConfig = mkOption {
+        type = types.attrs;
+        description = "Extra configuration for docspell server. Overwrites values in case of a conflict.";
+        default = { };
+        example = ''
+          {
+            files = {
+              default-store = "minio";
+              stores = {
+                minio = {
+                  enabled = true;
+                };
+              };
+            };
+          }
+        '';
+      };
     };
   };