diff --git a/nixos/modules/services/web-apps/freshrss.nix b/nixos/modules/services/web-apps/freshrss.nix
index 0e8bcc703efa..d67d927ba5ee 100644
--- a/nixos/modules/services/web-apps/freshrss.nix
+++ b/nixos/modules/services/web-apps/freshrss.nix
@@ -10,6 +10,7 @@ let
   };
   env-vars = {
     DATA_PATH = cfg.dataDir;
+  } // lib.optionalAttrs (cfg.extensions != []) {
     THIRDPARTY_EXTENSIONS_PATH = "${extension-env}/share/freshrss/";
   };
 in
diff --git a/pkgs/servers/web-apps/freshrss/default.nix b/pkgs/servers/web-apps/freshrss/default.nix
index e963b22fa302..99b4f7b2409a 100644
--- a/pkgs/servers/web-apps/freshrss/default.nix
+++ b/pkgs/servers/web-apps/freshrss/default.nix
@@ -21,10 +21,13 @@ stdenvNoCC.mkDerivation rec {
     patchShebangs cli/*.php app/actualize_script.php
   '';
 
-  # the thirdparty_extension_path can only be set by config, but should be read by an env-var.
+  # THIRDPARTY_EXTENSIONS_PATH can only be set by config, but should be read from an env-var.
   overrideConfig = writeText "constants.local.php" ''
     <?php
-      define('THIRDPARTY_EXTENSIONS_PATH', getenv('THIRDPARTY_EXTENSIONS_PATH') . '/extensions');
+      $thirdpartyExtensionsPath = getenv('THIRDPARTY_EXTENSIONS_PATH');
+      if (is_string($thirdpartyExtensionsPath) && $thirdpartyExtensionsPath !== "") {
+        define('THIRDPARTY_EXTENSIONS_PATH', $thirdpartyExtensionsPath . '/extensions');
+      }
   '';
 
   buildInputs = [ php ];