diff --git a/modules/programs/firefox/mkFirefoxModule.nix b/modules/programs/firefox/mkFirefoxModule.nix
index 1e6c87b11..733c8ec94 100644
--- a/modules/programs/firefox/mkFirefoxModule.nix
+++ b/modules/programs/firefox/mkFirefoxModule.nix
@@ -401,7 +401,7 @@ in {
           };
 
           userChrome = mkOption {
-            type = types.lines;
+            type = types.oneOf [ types.lines types.path ];
             default = "";
             description = "Custom ${appName} user chrome CSS.";
             example = ''
@@ -420,7 +420,7 @@ in {
           };
 
           userContent = mkOption {
-            type = types.lines;
+            type = types.oneOf [ types.lines types.path ];
             default = "";
             description = "Custom ${appName} user content CSS.";
             example = ''
@@ -868,10 +868,18 @@ in {
         "${profilesPath}/${profile.path}/.keep".text = "";
 
         "${profilesPath}/${profile.path}/chrome/userChrome.css" =
-          mkIf (profile.userChrome != "") { text = profile.userChrome; };
+          mkIf (profile.userChrome != "") (let
+            key =
+              if builtins.isString profile.userChrome then "text" else "source";
+          in { "${key}" = profile.userChrome; });
 
         "${profilesPath}/${profile.path}/chrome/userContent.css" =
-          mkIf (profile.userContent != "") { text = profile.userContent; };
+          mkIf (profile.userContent != "") (let
+            key = if builtins.isString profile.userContent then
+              "text"
+            else
+              "source";
+          in { "${key}" = profile.userContent; });
 
         "${profilesPath}/${profile.path}/user.js" = mkIf (profile.preConfig
           != "" || profile.settings != { } || profile.extraConfig != ""