diff --git a/pkgs/by-name/li/libtasn1/package.nix b/pkgs/by-name/li/libtasn1/package.nix
index 3bd5a828f519..8e27bac39404 100644
--- a/pkgs/by-name/li/libtasn1/package.nix
+++ b/pkgs/by-name/li/libtasn1/package.nix
@@ -35,8 +35,9 @@ stdenv.mkDerivation (finalAttrs: {
   strictDeps = true;
 
   doCheck = true;
-  preCheck =
-    if stdenv.hostPlatform.isDarwin then "export DYLD_LIBRARY_PATH=`pwd`/lib/.libs" else null;
+  preCheck = lib.optionalString stdenv.hostPlatform.isDarwin ''
+    export DYLD_LIBRARY_PATH=$(pwd)/lib/.libs
+  '';
 
   passthru.tests = {
     inherit gnutls samba qemu;