diff --git a/agent.cc b/agent.cc
index 6107e2a..e7446a6 100644
--- a/agent.cc
+++ b/agent.cc
@@ -106,6 +106,9 @@ agent::on_action_takes(void)
 void
 agent::on_tick(void)
 {
+	if (!tile)
+		return;
+
 	if (!dead) {
 		chenergy(world::sun_energy);