diff --git a/pkgs/applications/emulators/cdemu/libmirage.nix b/pkgs/applications/emulators/cdemu/libmirage.nix
index 257ce5ea44ac..e2017be9616c 100644
--- a/pkgs/applications/emulators/cdemu/libmirage.nix
+++ b/pkgs/applications/emulators/cdemu/libmirage.nix
@@ -34,8 +34,11 @@ in
 stdenv.mkDerivation {
   inherit pname version src;
 
-  PKG_CONFIG_GOBJECT_INTROSPECTION_1_0_GIRDIR = "${placeholder "out"}/share/gir-1.0";
-  PKG_CONFIG_GOBJECT_INTROSPECTION_1_0_TYPELIBDIR = "${placeholder "out"}/lib/girepository-1.0";
+  env = {
+    PKG_CONFIG_GOBJECT_INTROSPECTION_1_0_GIRDIR = "${placeholder "out"}/share/gir-1.0";
+    PKG_CONFIG_GOBJECT_INTROSPECTION_1_0_TYPELIBDIR = "${placeholder "out"}/lib/girepository-1.0";
+  };
+
   buildInputs = [
     glib
     libsndfile