diff --git a/src/route.h b/src/route.h
index 721953a9..6be2e1ea 100644
--- a/src/route.h
+++ b/src/route.h
@@ -120,7 +120,7 @@ struct rt {
 #define	RTDF_GATELINK		0x40		/* Gateway is on link */
 	size_t			rt_order;
 	rb_node_t		rt_tree;
-	int			rt_expires;	/* current lifetime of route */
+	uint32_t		rt_expires;	/* current lifetime of route */
 };
 
 extern const rb_tree_ops_t rt_compare_list_ops;