diff --git a/code/modules/economy/cash_register.dm b/code/modules/economy/cash_register.dm
index 1e065eb079..8184229c8b 100644
--- a/code/modules/economy/cash_register.dm
+++ b/code/modules/economy/cash_register.dm
@@ -122,7 +122,7 @@
 				transaction_purpose = t_purpose
 				item_list += t_purpose
 				var/t_amount = round(input("Enter price", "New price") as num)
-				if (!t_amount || !Adjacent(usr)) return
+				if (!t_amount || !Adjacent(usr) || t_amount < 0) return
 				transaction_amount += t_amount
 				price_list += t_amount
 				playsound(src, 'sound/machines/twobeep.ogg', 25)