diff --git a/pkgs/by-name/st/step-kms-plugin/package.nix b/pkgs/by-name/st/step-kms-plugin/package.nix
index 5a061773979f..e06231993204 100644
--- a/pkgs/by-name/st/step-kms-plugin/package.nix
+++ b/pkgs/by-name/st/step-kms-plugin/package.nix
@@ -42,7 +42,7 @@ buildGoModule rec {
     "-X github.com/smallstep/step-kms-plugin/cmd.Version=${version}"
   ];
 
-  CGO_CFLAGS = "-I${lib.getDev pcsclite}/include/PCSC/";
+  env.CGO_CFLAGS = "-I${lib.getDev pcsclite}/include/PCSC/";
 
   meta = {
     description = "Step plugin to manage keys and certificates on cloud KMSs and HSMs";