--- libs/ardour/plugin_insert.cc	(revision 9773)
+++ libs/ardour/plugin_insert.cc	(working copy)
@@ -884,6 +884,11 @@
 
 	uint32_t count = 1;
 
+	// may not exist for legacy 3.0 sessions
+	if ((prop = node.property ("id")) != 0) {
+		_id = prop->value();
+	}
+
 	if (_plugins.empty()) {
 		/* if we are adding the first plugin, we will need to set
 		   up automatable controls.