diff --git a/pkgs/development/python-modules/graphviz/default.nix b/pkgs/development/python-modules/graphviz/default.nix
index 49d7d3d68b34..8e45bdfd03ea 100644
--- a/pkgs/development/python-modules/graphviz/default.nix
+++ b/pkgs/development/python-modules/graphviz/default.nix
@@ -36,7 +36,7 @@ buildPythonPackage rec {
   ];
 
   # Fontconfig error: Cannot load default config file
-  FONTCONFIG_FILE = makeFontsConf { fontDirectories = [ freefont_ttf ]; };
+  env.FONTCONFIG_FILE = makeFontsConf { fontDirectories = [ freefont_ttf ]; };
 
   build-system = [ setuptools ];