diff --git a/pkgs/development/libraries/nss/default.nix b/pkgs/development/libraries/nss/default.nix
index e23aff9fcd83..3448527e17a5 100644
--- a/pkgs/development/libraries/nss/default.nix
+++ b/pkgs/development/libraries/nss/default.nix
@@ -106,7 +106,7 @@ in stdenv.mkDerivation rec {
     runHook postBuild
   '';
 
-  NIX_CFLAGS_COMPILE = "-Wno-error -DNIX_NSS_LIBDIR=\"${placeholder "out"}/lib/\"";
+  NIX_CFLAGS_COMPILE = "-Wno-error -DNIX_NSS_LIBDIR=\"${placeholder "out"}/lib/\" " + lib.optionalString stdenv.hostPlatform.is64bit "-DNSS_USE_64=1";
 
   installPhase = ''
     runHook preInstall