diff --git a/libempathy-gtk/empathy-chat.c b/libempathy-gtk/empathy-chat.c
index ca137d2..5a4ccd7 100644
--- a/libempathy-gtk/empathy-chat.c
+++ b/libempathy-gtk/empathy-chat.c
@@ -579,6 +579,7 @@ chat_property_changed_cb (EmpathyTpChat *tp_chat,
 			gtk_widget_hide (priv->hbox_topic);
 		} else {
 			gtk_label_set_text (GTK_LABEL (priv->label_topic), priv->subject);
+			gtk_widget_set_tooltip_text (priv->label_topic, priv->subject);
 			gtk_widget_show (priv->hbox_topic);
 		}
 		if (priv->block_events_timeout_id == 0) {
