diff --git a/Workshoppa/Windows/CeruleumTankWindow.cs b/Workshoppa/Windows/CeruleumTankWindow.cs
index e8f2cca..b83e875 100644
--- a/Workshoppa/Windows/CeruleumTankWindow.cs
+++ b/Workshoppa/Windows/CeruleumTankWindow.cs
@@ -106,10 +106,12 @@ internal sealed class CeruleumTankWindow : ShopWindow
         if (PurchaseState != null)
         {
             HandleNextPurchaseStep();
-
-            ImGui.Text($"Buying {FormatStackCount(PurchaseState.ItemsLeftToBuy)}...");
-            if (ImGuiComponents.IconButtonWithText(FontAwesomeIcon.Times, "Cancel Auto-Buy"))
-                CancelAutoPurchase();
+            if (PurchaseState != null)
+            {
+                ImGui.Text($"Buying {FormatStackCount(PurchaseState.ItemsLeftToBuy)}...");
+                if (ImGuiComponents.IconButtonWithText(FontAwesomeIcon.Times, "Cancel Auto-Buy"))
+                    CancelAutoPurchase();
+            }
         }
         else
         {
diff --git a/Workshoppa/Windows/RepairKitWindow.cs b/Workshoppa/Windows/RepairKitWindow.cs
index 5c7d3a2..59509f2 100644
--- a/Workshoppa/Windows/RepairKitWindow.cs
+++ b/Workshoppa/Windows/RepairKitWindow.cs
@@ -101,9 +101,11 @@ internal sealed class RepairKitWindow : ShopWindow
         if (PurchaseState != null)
         {
             HandleNextPurchaseStep();
-
-            if (ImGuiComponents.IconButtonWithText(FontAwesomeIcon.Times, "Cancel Auto-Buy"))
-                CancelAutoPurchase();
+            if (PurchaseState != null)
+            {
+                if (ImGuiComponents.IconButtonWithText(FontAwesomeIcon.Times, "Cancel Auto-Buy"))
+                    CancelAutoPurchase();
+            }
         }
         else
         {
diff --git a/Workshoppa/Windows/ShopWindow.cs b/Workshoppa/Windows/ShopWindow.cs
index 153fb10..8e7f700 100644
--- a/Workshoppa/Windows/ShopWindow.cs
+++ b/Workshoppa/Windows/ShopWindow.cs
@@ -157,7 +157,8 @@ internal abstract class ShopWindow : LImGui.LWindow, IDisposable
         if (ItemForSale == null || PurchaseState == null)
             return;
 
-        if (!_plugin.HasFreeInventorySlot())
+        int maxStackSize = _plugin.DetermineMaxStackSize(ItemForSale.ItemId);
+        if (maxStackSize == 0 && !_plugin.HasFreeInventorySlot())
         {
             _pluginLog.Warning($"No free inventory slots, can't buy more {ItemForSale.ItemName}");
             PurchaseState = null;
@@ -168,7 +169,7 @@ internal abstract class ShopWindow : LImGui.LWindow, IDisposable
             if (PurchaseState.NextStep <= DateTime.Now &&
                 _gameGui.TryGetAddonByName(_addonName, out AtkUnitBase* addonShop))
             {
-                int buyNow = Math.Min(PurchaseState.ItemsLeftToBuy, 99);
+                int buyNow = Math.Min(PurchaseState.ItemsLeftToBuy, maxStackSize);
                 _pluginLog.Information($"Buying {buyNow}x {ItemForSale.ItemName}");
 
                 FirePurchaseCallback(addonShop, buyNow);
diff --git a/Workshoppa/WorkshopPlugin.GameFunctions.cs b/Workshoppa/WorkshopPlugin.GameFunctions.cs
index 9e45111..73fb70c 100644
--- a/Workshoppa/WorkshopPlugin.GameFunctions.cs
+++ b/Workshoppa/WorkshopPlugin.GameFunctions.cs
@@ -42,7 +42,8 @@ partial class WorkshopPlugin
                     if (npcIds.Contains(GetNpcId(obj)))
                     {
                         o = obj;
-                        float distance = Vector3.Distance(localPlayerPosition.Value, obj.Position + new Vector3(0, -2, 0));
+                        float distance = Vector3.Distance(localPlayerPosition.Value,
+                            obj.Position + new Vector3(0, -2, 0));
                         if (distance > 0.01)
                             return distance;
                     }
@@ -62,7 +63,8 @@ partial class WorkshopPlugin
 
     private unsafe AtkUnitBase* GetCompanyCraftingLogAddon()
     {
-        if (_gameGui.TryGetAddonByName<AtkUnitBase>("CompanyCraftRecipeNoteBook", out var addon) && LAddon.IsAddonReady(addon))
+        if (_gameGui.TryGetAddonByName<AtkUnitBase>("CompanyCraftRecipeNoteBook", out var addon) &&
+            LAddon.IsAddonReady(addon))
             return addon;
 
         return null;
@@ -244,4 +246,32 @@ partial class WorkshopPlugin
 
         return count;
     }
+
+    public unsafe int DetermineMaxStackSize(uint itemId)
+    {
+        var inventoryManger = InventoryManager.Instance();
+        if (inventoryManger == null)
+            return 0;
+
+        int max = 0;
+        for (InventoryType t = InventoryType.Inventory1; t <= InventoryType.Inventory4; ++t)
+        {
+            var container = inventoryManger->GetInventoryContainer(t);
+            for (int i = 0; i < container->Size; ++i)
+            {
+                var item = container->GetInventorySlot(i);
+                if (item == null || item->ItemID == 0)
+                    return 99;
+
+                if (item->ItemID == itemId)
+                {
+                    max += (999 - (int)item->Quantity);
+                    if (max >= 99)
+                        break;
+                }
+            }
+        }
+
+        return Math.Min(99, max);
+    }
 }
diff --git a/Workshoppa/Workshoppa.csproj b/Workshoppa/Workshoppa.csproj
index d66f6eb..5615527 100644
--- a/Workshoppa/Workshoppa.csproj
+++ b/Workshoppa/Workshoppa.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
         <TargetFramework>net7.0-windows</TargetFramework>
-        <Version>3.7</Version>
+        <Version>3.8</Version>
         <LangVersion>11.0</LangVersion>
         <Nullable>enable</Nullable>
         <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>