diff --git a/pkgs/development/libraries/ucl/default.nix b/pkgs/development/libraries/ucl/default.nix
index ceb97b6088bc..aa983b1394b1 100644
--- a/pkgs/development/libraries/ucl/default.nix
+++ b/pkgs/development/libraries/ucl/default.nix
@@ -1,4 +1,4 @@
-{stdenv, fetchurl}:
+{ stdenv, fetchurl }:
 
 stdenv.mkDerivation {
   name = "ucl-1.03";
@@ -8,7 +8,7 @@ stdenv.mkDerivation {
   };
 
   # needed to successfully compile with gcc 6
-  NIX_CFLAGS_COMPILE = "-std=c90 -fPIC";
+  NIX_CFLAGS_COMPILE = stdenv.lib.optionalString stdenv.cc.isGNU "-std=c90";
 
   meta = {
     homepage = http://www.oberhumer.com/opensource/ucl/;