diff --git a/pkgs/development/python-modules/svgdigitizer/default.nix b/pkgs/development/python-modules/svgdigitizer/default.nix
index 99e363c86928..1e44d9a5f7d7 100644
--- a/pkgs/development/python-modules/svgdigitizer/default.nix
+++ b/pkgs/development/python-modules/svgdigitizer/default.nix
@@ -59,7 +59,7 @@ buildPythonPackage rec {
     svgwrite
   ];
   # https://github.com/echemdb/svgdigitizer/issues/252
-  MPLBACKEND = "Agg";
+  env.MPLBACKEND = "Agg";
 
   nativeCheckInputs = [
     pytestCheckHook