diff --git a/src/upnp.cpp b/src/upnp.cpp
index 002717672..c4f877f24 100644
--- a/src/upnp.cpp
+++ b/src/upnp.cpp
@@ -778,6 +778,9 @@ void upnp::update_map(rootdevice& d, int const i)
 
 	if (d.upnp_connection) return;
 
+	// this should not happen, but in case it does, don't fail at runtime
+	if (i >= d.mapping.end_index()) return;
+
 	std::shared_ptr<upnp> me(self());
 
 	mapping_t& m = d.mapping[i];