diff --git a/pkgs/development/ruby-modules/gem/default.nix b/pkgs/development/ruby-modules/gem/default.nix
index 20667988548c..c8dba5142082 100644
--- a/pkgs/development/ruby-modules/gem/default.nix
+++ b/pkgs/development/ruby-modules/gem/default.nix
@@ -217,8 +217,8 @@ stdenv.mkDerivation ((builtins.removeAttrs attrs ["source"]) // {
 
     # looks like useless files which break build repeatability and consume space
     pushd $out/${ruby.gemPath}
-    rm -fv doc/*/*/created.rid || true
-    rm -fv {gems/*/ext/*,extensions/*/*/*}/{Makefile,mkmf.log,gem_make.out} || true
+    find doc/ -iname created.rid -delete -print
+    find gems/*/ext/ extensions/ \( -iname Makefile -o -iname mkmf.log -o -iname gem_make.out \) -delete -print
     ${if keepGemCache then "" else "rm -fvr cache"}
     popd