Index: ext/extconf.rb
--- ext/extconf.rb.orig
+++ ext/extconf.rb
@@ -29,7 +29,7 @@ end
 # see: https://github.com/sass/sassc-ruby/issues/148
 enable_lto_by_default = (Gem::Platform.local.os == "darwin" && !ENV['NIX_CC'].nil?)
 
-if enable_config('lto', enable_lto_by_default)
+if enable_config('lto', false)
   $CFLAGS << ' -flto'
   $CXXFLAGS << ' -flto'
   $LDFLAGS << ' -flto'