diff --git a/pkgs/development/libraries/librsb/default.nix b/pkgs/development/libraries/librsb/default.nix
index e878e84e8d18..83caf9d4ac24 100644
--- a/pkgs/development/libraries/librsb/default.nix
+++ b/pkgs/development/libraries/librsb/default.nix
@@ -45,14 +45,16 @@ stdenv.mkDerivation rec {
   ];
 
   # Ensure C/Fortran code is position-independent.
-  env.NIX_CFLAGS_COMPILE = toString [
-    "-fPIC"
-    "-Ofast"
-  ];
-  FCFLAGS = [
-    "-fPIC"
-    "-Ofast"
-  ];
+  env = {
+    NIX_CFLAGS_COMPILE = toString [
+      "-fPIC"
+      "-Ofast"
+    ];
+    FCFLAGS = toString [
+      "-fPIC"
+      "-Ofast"
+    ];
+  };
 
   enableParallelBuilding = true;