diff --git a/pkgs/build-support/pkg-config-wrapper/default.nix b/pkgs/build-support/pkg-config-wrapper/default.nix
index 3f2ec688dd3d..da77765f82d3 100644
--- a/pkgs/build-support/pkg-config-wrapper/default.nix
+++ b/pkgs/build-support/pkg-config-wrapper/default.nix
@@ -59,7 +59,7 @@ stdenv.mkDerivation {
   dontUnpack = true;
 
   # Additional flags passed to pkg-config.
-  addFlags = optional stdenv.targetPlatform.isStatic "--static";
+  env.addFlags = optionalString stdenv.targetPlatform.isStatic "--static";
 
   installPhase =
     ''