diff --git a/passes/techmap/iopadmap.cc b/passes/techmap/iopadmap.cc
index 4acbf7c0d..15ad51c87 100644
--- a/passes/techmap/iopadmap.cc
+++ b/passes/techmap/iopadmap.cc
@@ -312,7 +312,7 @@ struct IopadmapPass : public Pass {
 				if (!portname2.empty()) {
 					new_wire = module->addWire(NEW_ID, wire);
 					module->swap_names(new_wire, wire);
-					wire->attributes.clear();
+					new_wire->attributes.swap(wire->attributes);
 				}
 
 				if (flag_bits)