diff --git a/libs/ardour/io.cc b/libs/ardour/io.cc
index 5af985b50e..9b567e841d 100644
--- a/libs/ardour/io.cc
+++ b/libs/ardour/io.cc
@@ -615,7 +615,7 @@ IO::set_state (const XMLNode& node, int version)
 		 */
 		PortSet::iterator i = _ports.begin();
 		XMLNodeConstIterator x = node.children().begin();
-		for (; i != _ports.end(), x != node.children().end(); ++i, ++x) {
+		for (; i != _ports.end() && x != node.children().end(); ++i, ++x) {
 			if ((*x)->name() == "Port") {
 				(*x)->remove_property (X_("name"));
 				(*x)->set_property (X_("name"), i->name());