diff --git a/techlibs/ice40/ice40_opt.cc b/techlibs/ice40/ice40_opt.cc
index b13d33018..c88fd69b6 100644
--- a/techlibs/ice40/ice40_opt.cc
+++ b/techlibs/ice40/ice40_opt.cc
@@ -117,7 +117,7 @@ static void run_ice40_opts(Module *module)
 
 			if (GetSize(replacement_output)) {
 				optimized_co.insert(sigmap(cell->getPort(ID::CO)[0]));
-				auto it = cell->attributes.find(ID(SB_LUT4.name));
+				auto it = cell->attributes.find(IdString{"\\SB_LUT4.name"});
 				if (it != cell->attributes.end()) {
 					module->rename(cell, it->second.decode_string());
 					decltype(Cell::attributes) new_attr;
@@ -126,7 +126,7 @@ static void run_ice40_opts(Module *module)
 							new_attr[a.first.c_str() + strlen("\\SB_LUT4.")] = a.second;
 						else if (a.first == ID::src)
 							new_attr.insert(std::make_pair(a.first, a.second));
-						else if (a.first.in(ID(SB_LUT4.name), ID::keep, ID::module_not_derived))
+						else if (a.first.in(IdString{"\\SB_LUT4.name"}, ID::keep, ID::module_not_derived))
 							continue;
 						else if (a.first.begins_with("\\SB_CARRY.\\"))
 							continue;
diff --git a/techlibs/ice40/ice40_wrapcarry.cc b/techlibs/ice40/ice40_wrapcarry.cc
index fe928ba6d..82218ff11 100644
--- a/techlibs/ice40/ice40_wrapcarry.cc
+++ b/techlibs/ice40/ice40_wrapcarry.cc
@@ -62,7 +62,7 @@ void create_ice40_wrapcarry(ice40_wrapcarry_pm &pm)
 		cell->attributes[stringf("\\SB_CARRY.%s", a.first)] = a.second;
 	for (const auto &a : st.lut->attributes)
 		cell->attributes[stringf("\\SB_LUT4.%s", a.first)] = a.second;
-	cell->attributes[ID(SB_LUT4.name)] = Const(st.lut->name.str());
+	cell->attributes[IdString{"\\SB_LUT4.name"}] = Const(st.lut->name.str());
 	if (st.carry->get_bool_attribute(ID::keep) || st.lut->get_bool_attribute(ID::keep))
 		cell->attributes[ID::keep] = true;
 
@@ -122,7 +122,7 @@ struct Ice40WrapCarryPass : public Pass {
 					carry->setPort(ID::CI, cell->getPort(ID::CI));
 					carry->setPort(ID::CO, cell->getPort(ID::CO));
 					module->swap_names(carry, cell);
-					auto lut_name = cell->attributes.at(ID(SB_LUT4.name), Const(NEW_ID.str())).decode_string();
+					auto lut_name = cell->attributes.at(IdString{"\\SB_LUT4.name"}, Const(NEW_ID.str())).decode_string();
 					auto lut = module->addCell(lut_name, ID($lut));
 					lut->setParam(ID::WIDTH, 4);
 					lut->setParam(ID::LUT, cell->getParam(ID::LUT));
@@ -138,7 +138,7 @@ struct Ice40WrapCarryPass : public Pass {
 							lut->attributes[a.first.c_str() + strlen("\\SB_LUT4.")] = a.second;
 						else if (a.first == ID::src)
 							src = a.second;
-						else if (a.first.in(ID(SB_LUT4.name), ID::keep, ID::module_not_derived))
+						else if (a.first.in(IdString{"\\SB_LUT4.name"}, ID::keep, ID::module_not_derived))
 							continue;
 						else
 							log_abort();