diff --git a/package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh b/package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh
index ffb3662d04..0b7a84d7c9 100644
--- a/package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh
+++ b/package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh
@@ -1190,6 +1190,10 @@ drv_mac80211_teardown() {
 	json_select data
 	json_get_vars phy
 	json_select ..
+	[ -n "$phy" ] || {
+		echo "Bug: PHY is undefined for device '$1'"
+		return 1
+	}
 
 	mac80211_interface_cleanup "$phy"
 	uci -q -P /var/state revert wireless._${phy}