diff --git a/pkgs/development/tools/pew/default.nix b/pkgs/development/tools/pew/default.nix
index 73046165b1a..7ad68d8844b 100644
--- a/pkgs/development/tools/pew/default.nix
+++ b/pkgs/development/tools/pew/default.nix
@@ -11,6 +11,8 @@ with python3Packages; buildPythonApplication rec {
 
     propagatedBuildInputs = [ virtualenv virtualenv-clone setuptools ];
 
+    LC_ALL = "en_US.UTF-8";
+
     postFixup = ''
       set -euo pipefail
       PEW_SITE="$out/lib/${python.libPrefix}/site-packages"