diff --git a/src/main/java/com/Acrobot/ChestShop/Configuration/Messages.java b/src/main/java/com/Acrobot/ChestShop/Configuration/Messages.java
index 3160f01..5f282c7 100644
--- a/src/main/java/com/Acrobot/ChestShop/Configuration/Messages.java
+++ b/src/main/java/com/Acrobot/ChestShop/Configuration/Messages.java
@@ -48,6 +48,8 @@ public class Messages {
     public static String YOU_CANNOT_CREATE_SHOP = "You can't create this type of shop!";
     public static String NO_CHEST_DETECTED = "Couldn't find a chest!";
     public static String INVALID_SHOP_DETECTED = "The shop cannot be used!";
+    public static String INVALID_SHOP_PRICE = "The shop has an invalid price!";
+    public static String INVALID_SHOP_QUANTITY = "The shop has an invalid quantity!";
     public static String CANNOT_ACCESS_THE_CHEST = "You don't have permissions to access this chest!";
 
     @PrecededBySpace
diff --git a/src/main/java/com/Acrobot/ChestShop/Configuration/Properties.java b/src/main/java/com/Acrobot/ChestShop/Configuration/Properties.java
index ad5c16c..7b56813 100644
--- a/src/main/java/com/Acrobot/ChestShop/Configuration/Properties.java
+++ b/src/main/java/com/Acrobot/ChestShop/Configuration/Properties.java
@@ -72,6 +72,10 @@ public class Properties {
     @ConfigurationComment("Should we block shops that sell things for more than they buy? (This prevents newbies from creating shops that would be exploited)")
     public static boolean BLOCK_SHOPS_WITH_SELL_PRICE_HIGHER_THAN_BUY_PRICE = true;
 
+    @PrecededBySpace
+    @ConfigurationComment("Maximum amount of items that can be bought/sold at a shop. Default 3456 is a double chest of 64 stacks.")
+    public static int MAX_SHOP_AMOUNT = 3456;
+
     @PrecededBySpace
     @ConfigurationComment("Do you want to allow other players to build a shop on a block where there's one already?")
     public static boolean ALLOW_MULTIPLE_SHOPS_AT_ONE_BLOCK = false;
diff --git a/src/main/java/com/Acrobot/ChestShop/Listeners/Player/PlayerInteract.java b/src/main/java/com/Acrobot/ChestShop/Listeners/Player/PlayerInteract.java
index ef5fd24..c6656ac 100644
--- a/src/main/java/com/Acrobot/ChestShop/Listeners/Player/PlayerInteract.java
+++ b/src/main/java/com/Acrobot/ChestShop/Listeners/Player/PlayerInteract.java
@@ -168,10 +168,14 @@ public class PlayerInteract implements Listener {
             return null;
         }
 
-        int amount = Integer.parseInt(quantity);
+        int amount = -1;
+        try {
+            amount = Integer.parseInt(quantity);
+        } catch (NumberFormatException notANumber) {}
 
-        if (amount < 1) {
-            amount = 1;
+        if (amount < 1 || amount > Properties.MAX_SHOP_AMOUNT) {
+            player.sendMessage(Messages.prefix(Messages.INVALID_SHOP_PRICE));
+            return null;
         }
 
         if (Properties.SHIFT_SELLS_IN_STACKS && player.isSneaking() && price != PriceUtil.NO_PRICE && isAllowedForShift(action == buy)) {
diff --git a/src/main/java/com/Acrobot/ChestShop/Listeners/PreShopCreation/ErrorMessageSender.java b/src/main/java/com/Acrobot/ChestShop/Listeners/PreShopCreation/ErrorMessageSender.java
index 7815acc..37ef334 100644
--- a/src/main/java/com/Acrobot/ChestShop/Listeners/PreShopCreation/ErrorMessageSender.java
+++ b/src/main/java/com/Acrobot/ChestShop/Listeners/PreShopCreation/ErrorMessageSender.java
@@ -24,10 +24,10 @@ public class ErrorMessageSender implements Listener {
                 message = Messages.INCORRECT_ITEM_ID;
                 break;
             case INVALID_PRICE:
-                message = Messages.INVALID_SHOP_DETECTED;
+                message = Messages.INVALID_SHOP_PRICE;
                 break;
             case INVALID_QUANTITY:
-                message = Messages.INVALID_SHOP_DETECTED;
+                message = Messages.INVALID_SHOP_QUANTITY;
                 break;
             case SELL_PRICE_HIGHER_THAN_BUY_PRICE:
                 message = Messages.YOU_CANNOT_CREATE_SHOP;
diff --git a/src/main/java/com/Acrobot/ChestShop/Listeners/PreShopCreation/QuantityChecker.java b/src/main/java/com/Acrobot/ChestShop/Listeners/PreShopCreation/QuantityChecker.java
index 50053b7..2d93841 100644
--- a/src/main/java/com/Acrobot/ChestShop/Listeners/PreShopCreation/QuantityChecker.java
+++ b/src/main/java/com/Acrobot/ChestShop/Listeners/PreShopCreation/QuantityChecker.java
@@ -1,6 +1,6 @@
 package com.Acrobot.ChestShop.Listeners.PreShopCreation;
 
-import com.Acrobot.Breeze.Utils.NumberUtil;
+import com.Acrobot.ChestShop.Configuration.Properties;
 import com.Acrobot.ChestShop.Events.PreShopCreationEvent;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.EventPriority;
@@ -16,9 +16,12 @@ public class QuantityChecker implements Listener {
 
     @EventHandler(priority = EventPriority.LOWEST)
     public static void onPreShopCreation(PreShopCreationEvent event) {
-        String quantity = event.getSignLine(QUANTITY_LINE);
+        int amount = -1;
+        try {
+            amount = Integer.parseInt(event.getSignLine(QUANTITY_LINE));
+        } catch (NumberFormatException notANumber) {}
 
-        if (!NumberUtil.isInteger(quantity)) {
+        if (amount < 1 || amount > Properties.MAX_SHOP_AMOUNT) {
             event.setOutcome(INVALID_QUANTITY);
         }
     }
diff --git a/src/main/java/com/Acrobot/ChestShop/Signs/ChestShopSign.java b/src/main/java/com/Acrobot/ChestShop/Signs/ChestShopSign.java
index 96aa5a5..114d1d4 100644
--- a/src/main/java/com/Acrobot/ChestShop/Signs/ChestShopSign.java
+++ b/src/main/java/com/Acrobot/ChestShop/Signs/ChestShopSign.java
@@ -27,7 +27,7 @@ public class ChestShopSign {
 
     public static final Pattern[] SHOP_SIGN_PATTERN = {
             Pattern.compile("^?[\\w -.:]*$"),
-            Pattern.compile("^[1-9][0-9]*$"),
+            Pattern.compile("^[1-9][0-9]{0,6}$"),
             Pattern.compile("(?i)^[\\d.bs(free) :]+$"),
             Pattern.compile("^[\\w? #:-]+$")
     };