diff --git a/pkgs/by-name/li/lilypond/package.nix b/pkgs/by-name/li/lilypond/package.nix
index c81b8a6df53d..3c583d8d96e9 100644
--- a/pkgs/by-name/li/lilypond/package.nix
+++ b/pkgs/by-name/li/lilypond/package.nix
@@ -147,7 +147,11 @@ stdenv.mkDerivation (finalAttrs: {
     platforms = lib.platforms.all;
   };
 
-  FONTCONFIG_FILE = lib.optional stdenv.hostPlatform.isDarwin (makeFontsConf {
-    fontDirectories = [ freefont_ttf ];
-  });
+  env = lib.optionalAttrs stdenv.hostPlatform.isDarwin {
+    FONTCONFIG_FILE = (
+      makeFontsConf {
+        fontDirectories = [ freefont_ttf ];
+      }
+    );
+  };
 })