diff --git a/pkgs/development/interpreters/ruby/gem.nix b/pkgs/development/interpreters/ruby/gem.nix
index ed898b65400..dcef9ab592f 100644
--- a/pkgs/development/interpreters/ruby/gem.nix
+++ b/pkgs/development/interpreters/ruby/gem.nix
@@ -70,8 +70,8 @@ in ruby.stdenv.mkDerivation (attrs // {
     done
 
     # looks like useless files which break build repeatability and consume space
-    rm $out/${ruby.gemPath}/doc/*/*/created.rid || true
-    rm $out/${ruby.gemPath}/gems/*/ext/*/mkmf.log || true
+    rm -f $out/${ruby.gemPath}/doc/*/*/created.rid || true
+    rm -f $out/${ruby.gemPath}/gems/*/ext/*/mkmf.log || true
 
     mkdir -p $out/nix-support