diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index 1808f3fc1..1bcff2772 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -1700,7 +1700,7 @@ void RTLIL::Design::rename(RTLIL::Module *module, TwineRef new_name)
 void RTLIL::Design::sort()
 {
 	scratchpad.sort();
-	modules_.sort();
+	modules_.sort(sort_by_twine_str_expensive(twines));
 	for (auto &it : modules_)
 		it.second->sort();
 }
@@ -1708,7 +1708,7 @@ void RTLIL::Design::sort()
 void RTLIL::Design::sort_modules()
 {
 	scratchpad.sort();
-	modules_.sort();
+	modules_.sort(sort_by_twine_str_expensive(twines));
 }
 
 void check_module(RTLIL::Module *module, ParallelDispatchThreadPool &thread_pool);