diff --git a/pkgs/development/ruby-modules/gem/default.nix b/pkgs/development/ruby-modules/gem/default.nix
index 74dc64000c0..8015fb1f6d0 100644
--- a/pkgs/development/ruby-modules/gem/default.nix
+++ b/pkgs/development/ruby-modules/gem/default.nix
@@ -48,7 +48,7 @@ lib.makeOverridable (
 , dontBuild ? true
 , propagatedBuildInputs ? []
 , propagatedUserEnvPkgs ? []
-, buildFlags ? null
+, buildFlags ? []
 , passthru ? {}
 , ...} @ attrs: