diff --git a/modules/programs/firefox.nix b/modules/programs/firefox.nix
index 1370d4c2..d4da9477 100644
--- a/modules/programs/firefox.nix
+++ b/modules/programs/firefox.nix
@@ -60,7 +60,7 @@ let
     else
       builtins.toJSON pref);
 
-  mkUserJs = prefs: extraPrefs: bookmarks:
+  mkUserJs = prePrefs: prefs: extraPrefs: bookmarks:
     let
       prefs' = lib.optionalAttrs ([ ] != bookmarks) {
         "browser.bookmarks.file" = toString (firefoxBookmarksFile bookmarks);
@@ -69,6 +69,8 @@ let
     in ''
       // Generated by Home Manager.
 
+      ${prePrefs}
+
       ${concatStrings (mapAttrsToList (name: value: ''
         user_pref("${name}", ${userPrefValue value});
       '') prefs')}
@@ -305,6 +307,19 @@ in {
               '';
             };
 
+            preConfig = mkOption {
+              type = types.lines;
+              default = "";
+              description = ''
+                Extra preferences to add to {file}`user.js`, before
+                [{option}`programs.firefox.profiles.<profile>.settings`](#opt-programs.firefox.profiles._name_.settings).
+
+                Use [{option}`programs.firefox.profiles.<profile>.extraConfig`](#opt-programs.firefox.profiles._name_.extraConfig),
+                unless you want to overwrite in
+                [{option}`programs.firefox.profiles.<profile>.settings`](#opt-programs.firefox.profiles._name_.settings)
+              '';
+            };
+
             settings = mkOption {
               type = types.attrsOf (jsonFormat.type // {
                 description =
@@ -770,10 +785,11 @@ in {
       "${profilesPath}/${profile.path}/chrome/userContent.css" =
         mkIf (profile.userContent != "") { text = profile.userContent; };
 
-      "${profilesPath}/${profile.path}/user.js" = mkIf (profile.settings != { }
-        || profile.extraConfig != "" || profile.bookmarks != [ ]) {
-          text =
-            mkUserJs profile.settings profile.extraConfig profile.bookmarks;
+      "${profilesPath}/${profile.path}/user.js" = mkIf (profile.preConfig != ""
+        || profile.settings != { } || profile.extraConfig != ""
+        || profile.bookmarks != [ ]) {
+          text = mkUserJs profile.preConfig profile.settings profile.extraConfig
+            profile.bookmarks;
         };
 
       "${profilesPath}/${profile.path}/containers.json" =
diff --git a/tests/modules/programs/firefox/profile-settings-expected-bookmarks-user.js b/tests/modules/programs/firefox/profile-settings-expected-bookmarks-user.js
index 922d3651..8ffd7696 100644
--- a/tests/modules/programs/firefox/profile-settings-expected-bookmarks-user.js
+++ b/tests/modules/programs/firefox/profile-settings-expected-bookmarks-user.js
@@ -1,5 +1,7 @@
 // Generated by Home Manager.
 
+
+
 user_pref("browser.bookmarks.file", "/nix/store/00000000000000000000000000000000-firefox-bookmarks.html");
 user_pref("browser.places.importBookmarksHTML", true);
 user_pref("general.smoothScroll", false);
diff --git a/tests/modules/programs/firefox/profile-settings-expected-overwrite-user.js b/tests/modules/programs/firefox/profile-settings-expected-overwrite-user.js
new file mode 100644
index 00000000..cbcc5f26
--- /dev/null
+++ b/tests/modules/programs/firefox/profile-settings-expected-overwrite-user.js
@@ -0,0 +1,10 @@
+// Generated by Home Manager.
+
+user_pref("browser.search.suggest.enabled", false);
+
+
+user_pref("browser.search.suggest.enabled", true);
+
+
+user_pref("findbar.highlightAll", true);
+
diff --git a/tests/modules/programs/firefox/profile-settings-expected-user.js b/tests/modules/programs/firefox/profile-settings-expected-user.js
index d929df2b..8118d73b 100644
--- a/tests/modules/programs/firefox/profile-settings-expected-user.js
+++ b/tests/modules/programs/firefox/profile-settings-expected-user.js
@@ -1,5 +1,7 @@
 // Generated by Home Manager.
 
+
+
 user_pref("browser.newtabpage.pinned", "[{\"title\":\"NixOS\",\"url\":\"https://nixos.org\"}]");
 user_pref("general.smoothScroll", false);
 
diff --git a/tests/modules/programs/firefox/profile-settings.nix b/tests/modules/programs/firefox/profile-settings.nix
index 8b781552..7a83ed77 100644
--- a/tests/modules/programs/firefox/profile-settings.nix
+++ b/tests/modules/programs/firefox/profile-settings.nix
@@ -153,6 +153,17 @@
           };
         };
       };
+
+      profiles.overwrite = {
+        id = 6;
+        preConfig = ''
+          user_pref("browser.search.suggest.enabled", false);
+        '';
+        settings = { "browser.search.suggest.enabled" = true; };
+        extraConfig = ''
+          user_pref("findbar.highlightAll", true);
+        '';
+      };
     };
 
     nmt.script = ''
@@ -203,6 +214,10 @@
       assertFirefoxSearchContent \
         home-files/.mozilla/firefox/searchWithoutDefault/search.json.mozlz4 \
         ${./profile-settings-expected-search-without-default.json}
+
+      assertFileContent \
+        home-files/.mozilla/firefox/overwrite/user.js \
+        ${./profile-settings-expected-overwrite-user.js}
     '';
   };
 }