diff --git a/pkgs/development/tools/mutmut/default.nix b/pkgs/development/tools/mutmut/default.nix
index 4b40930c646d..85d981961d16 100644
--- a/pkgs/development/tools/mutmut/default.nix
+++ b/pkgs/development/tools/mutmut/default.nix
@@ -1,6 +1,7 @@
 { lib
 , fetchFromGitHub
 , python3
+, testers
 }:
 
 let self = with python3.pkgs; buildPythonApplication rec {