diff --git a/pkgs/development/interpreters/ruby/bundix.nix b/pkgs/development/interpreters/ruby/bundix.nix
index b4cc4bbb31f..f86190005bb 100644
--- a/pkgs/development/interpreters/ruby/bundix.nix
+++ b/pkgs/development/interpreters/ruby/bundix.nix
@@ -6,7 +6,7 @@
       expr = callPackage path {};
       ruby = config.ruby;
       rubyLibs = rubyLibsWith ruby;
-      gems = rubyLibs.importGems expr.gemset config.gemOverrides;
+      gems = rubyLibs.importGems gemset (config.gemOverrides or (gemset: {}));
     in {
       inherit ruby; # TODO: Set ruby using expr.rubyVersion if not given.
       gemPath = map (drv: "${drv}/${ruby.gemPath}") (