diff --git a/pkgs/development/python-modules/mitmproxy-linux/default.nix b/pkgs/development/python-modules/mitmproxy-linux/default.nix
index 0dd4551a55e4..342ef131b55b 100644
--- a/pkgs/development/python-modules/mitmproxy-linux/default.nix
+++ b/pkgs/development/python-modules/mitmproxy-linux/default.nix
@@ -26,8 +26,10 @@ buildPythonPackage {
     patch -p1 < tmp.diff
   '';
 
-  RUSTFLAGS = "-C target-feature=";
-  RUSTC_BOOTSTRAP = 1;
+  env = {
+    RUSTFLAGS = "-C target-feature=";
+    RUSTC_BOOTSTRAP = 1;
+  };
 
   buildAndTestSubdir = "mitmproxy-linux";