diff --git a/booking.manual_payment.inc b/booking.manual_payment.inc
index 6169b39..6b481ef 100644
--- a/booking.manual_payment.inc
+++ b/booking.manual_payment.inc
@@ -128,7 +128,7 @@ function booking_manual_payment_admin_submit($form, &$form_state) {
 	//watchdog('booking', 'Manual payment form contents: @info', array('@info' => var_export($form_state['values'], TRUE)));
 	
 	//check if there is a pre-defined payment type selected
-	if ($form_state['values']['payment-type'] != '' && $form_state['values']['payment-custom-amount'] == '0.00') {
+	if ((!empty($form_state['values']['payment-type'])) && $form_state['values']['payment-custom-amount'] == '0.00') {
 		//look up the price relating to the price id selected
 	    $price_query = db_query("SELECT price.booking_price, price.booking_late_price, price.booking_price_descrip " .
 					"FROM {booking_price} price " .