diff --git a/etc/inc/interfaces.inc b/etc/inc/interfaces.inc
index 48a8db9fa3..08a7be6b29 100644
--- a/etc/inc/interfaces.inc
+++ b/etc/inc/interfaces.inc
@@ -1519,6 +1519,7 @@ function get_wireless_modes($interface)
 		$stack_list = "$awk -F\"Channel \" '{print \$2 \"\\\n\" \$3 }'";
 		$format_list = "$awk '{print \$5 \" \" \$6 \",\" \$1}'";
 
+		$interface_channels = "";
 		exec("$chan_list | $stack_list | sort -u | $format_list 2>&1", $interface_channels);
 		$interface_channel_count = count($interface_channels);