diff --git a/pkgs/development/python-modules/cppe/default.nix b/pkgs/development/python-modules/cppe/default.nix
index 63c05e7998a7..5bbaffa08e05 100644
--- a/pkgs/development/python-modules/cppe/default.nix
+++ b/pkgs/development/python-modules/cppe/default.nix
@@ -42,7 +42,9 @@ buildPythonPackage {
 
   buildInputs = [ pybind11 ] ++ lib.optional stdenv.cc.isClang llvmPackages.openmp;
 
-  NIX_CFLAGS_LINK = lib.optional stdenv.cc.isClang "-lomp";
+  env = lib.optionalAttrs stdenv.cc.isClang {
+    NIX_CFLAGS_LINK = "-lomp";
+  };
 
   hardeningDisable = lib.optional stdenv.cc.isClang "strictoverflow";