diff --git a/modules/programs/firefox.nix b/modules/programs/firefox.nix
index bf1c5779..4b3f288c 100644
--- a/modules/programs/firefox.nix
+++ b/modules/programs/firefox.nix
@@ -42,6 +42,12 @@ let
 
   profilesIni = generators.toINI { } profiles;
 
+  userPrefValue = pref:
+    builtins.toJSON (if isBool pref || isInt pref || isString pref then
+      pref
+    else
+      builtins.toJSON pref);
+
   mkUserJs = prefs: extraPrefs: bookmarks:
     let
       prefs' = lib.optionalAttrs ([ ] != bookmarks) {
@@ -52,7 +58,7 @@ let
       // Generated by Home Manager.
 
       ${concatStrings (mapAttrsToList (name: value: ''
-        user_pref("${name}", ${builtins.toJSON value});
+        user_pref("${name}", ${userPrefValue value});
       '') prefs')}
 
       ${extraPrefs}
@@ -201,7 +207,10 @@ in {
             };
 
             settings = mkOption {
-              type = with types; attrsOf (either bool (either int str));
+              type = types.attrsOf (jsonFormat.type // {
+                description =
+                  "Firefox preference (int, bool, string, and also attrs, list, float as a JSON string)";
+              });
               default = { };
               example = literalExpression ''
                 {
@@ -211,9 +220,19 @@ in {
                   "distribution.searchplugins.defaultLocale" = "en-GB";
                   "general.useragent.locale" = "en-GB";
                   "browser.bookmarks.showMobileBookmarks" = true;
+                  "browser.newtabpage.pinned" = [{
+                    title = "NixOS";
+                    url = "https://nixos.org";
+                  }];
                 }
               '';
-              description = "Attribute set of Firefox preferences.";
+              description = ''
+                Attribute set of Firefox preferences.
+
+                Firefox only supports int, bool, and string types for
+                preferences, but home-manager will automatically
+                convert all other JSON-compatible values into strings.
+              '';
             };
 
             extraConfig = mkOption {
diff --git a/tests/modules/programs/firefox/profile-settings-expected-user.js b/tests/modules/programs/firefox/profile-settings-expected-user.js
index 0edd47b9..d929df2b 100644
--- a/tests/modules/programs/firefox/profile-settings-expected-user.js
+++ b/tests/modules/programs/firefox/profile-settings-expected-user.js
@@ -1,5 +1,6 @@
 // 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 b28e6459..278f3dbb 100644
--- a/tests/modules/programs/firefox/profile-settings.nix
+++ b/tests/modules/programs/firefox/profile-settings.nix
@@ -9,7 +9,13 @@ lib.mkIf config.test.enableBig {
 
     profiles.test = {
       id = 1;
-      settings = { "general.smoothScroll" = false; };
+      settings = {
+        "general.smoothScroll" = false;
+        "browser.newtabpage.pinned" = [{
+          title = "NixOS";
+          url = "https://nixos.org";
+        }];
+      };
     };
 
     profiles.bookmarks = {