diff --git a/frontends/ast/genrtlil.cc b/frontends/ast/genrtlil.cc
index 2f1e34a3a..96f589247 100644
--- a/frontends/ast/genrtlil.cc
+++ b/frontends/ast/genrtlil.cc
@@ -624,7 +624,7 @@ struct AST_INTERNAL::ProcessGenerator
 			if (inSyncRule && lvalue_c.wire && lvalue_c.wire->get_bool_attribute(ID::nosync))
 				rhs = RTLIL::SigSpec(RTLIL::State::Sx, rhs.size());
 			remove_unwanted_lvalue_bits(lhs, rhs);
-			actions.push_back({lhs, rhs, ast ? current_module->design->twines.add(std::string{ast->loc_string()}) : Twine::Null});
+			actions.push_back({lhs, rhs, ast ? current_module->design->twines.add(Twine{ast->loc_string()}) : Twine::Null});
 			offset += lhs.size();
 		}
 	}
@@ -680,7 +680,7 @@ struct AST_INTERNAL::ProcessGenerator
 						current_case_assigned_bits.insert(bit);
 
 				remove_unwanted_lvalue_bits(lvalue, rvalue);
-				current_case->actions.push_back({lvalue, rvalue, current_module->design->twines.add(std::string{ast->loc_string()})});
+				current_case->actions.push_back({lvalue, rvalue, current_module->design->twines.add(Twine{ast->loc_string()})});
 			}
 			break;
 
@@ -830,8 +830,8 @@ struct AST_INTERNAL::ProcessGenerator
 
 				Wire *en = current_module->addWire(current_module->design->twines.add(std::string{sstr.str() + "_EN"}), 1);
 				set_src_attr(en, ast);
-				proc->root_case.actions.push_back({en, SigSpec(false), current_module->design->twines.add(std::string{ast->loc_string()})});
-				current_case->actions.push_back({en, SigSpec(true), current_module->design->twines.add(std::string{ast->loc_string()})});
+				proc->root_case.actions.push_back({en, SigSpec(false), current_module->design->twines.add(Twine{ast->loc_string()})});
+				current_case->actions.push_back({en, SigSpec(true), current_module->design->twines.add(Twine{ast->loc_string()})});
 
 				RTLIL::SigSpec triggers;
 				RTLIL::Const::Builder polarity_builder;
@@ -928,8 +928,8 @@ struct AST_INTERNAL::ProcessGenerator
 
 				Wire *en = current_module->addWire(current_module->design->twines.add(std::string{cellname.str() + "_EN"}), 1);
 				set_src_attr(en, ast);
-				proc->root_case.actions.push_back({en, SigSpec(false), current_module->design->twines.add(std::string{ast->loc_string()})});
-				current_case->actions.push_back({en, SigSpec(true), current_module->design->twines.add(std::string{ast->loc_string()})});
+				proc->root_case.actions.push_back({en, SigSpec(false), current_module->design->twines.add(Twine{ast->loc_string()})});
+				current_case->actions.push_back({en, SigSpec(true), current_module->design->twines.add(Twine{ast->loc_string()})});
 
 				RTLIL::SigSpec triggers;
 				RTLIL::Const::Builder polarity_builder;