diff --git a/pkgs/development/libraries/nss/default.nix b/pkgs/development/libraries/nss/default.nix
index 137f47fe635..329b91f124b 100644
--- a/pkgs/development/libraries/nss/default.nix
+++ b/pkgs/development/libraries/nss/default.nix
@@ -28,7 +28,7 @@ stdenv.mkDerivation {
 
   makeFlags =
     ["NSPR_CONFIG_STATUS=" "NSDISTMODE=copy" "BUILD_OPT=1" "SOURCE_PREFIX=\$(out)"]
-    ++ stdenv.lib.optionals stdenv.is64bit "USE_64=1";
+    ++ stdenv.lib.optional stdenv.is64bit "USE_64=1";
 
   buildFlags = "nss_build_all";