diff --git a/source/ItemGrid.cpp b/source/ItemGrid.cpp
index a977a9b6d..e9b86173e 100644
--- a/source/ItemGrid.cpp
+++ b/source/ItemGrid.cpp
@@ -213,7 +213,7 @@ void cItemGrid::Clear(void)
 
 
 
-int cItemGrid::HowManyCanFit(const cItem & a_ItemStack)
+int cItemGrid::HowManyCanFit(const cItem & a_ItemStack, bool a_AllowNewStacks)
 {
 	char NumLeft = a_ItemStack.m_ItemCount;
 	int MaxStack = ItemHandler(a_ItemStack.m_ItemType)->GetMaxStackSize();
@@ -221,7 +221,10 @@ int cItemGrid::HowManyCanFit(const cItem & a_ItemStack)
 	{
 		if (m_Slots[i].IsEmpty())
 		{
-			NumLeft -= MaxStack;
+			if (a_AllowNewStacks)
+			{
+				NumLeft -= MaxStack;
+			}
 		}
 		else if (m_Slots[i].IsStackableWith(a_ItemStack))
 		{
diff --git a/source/ItemGrid.h b/source/ItemGrid.h
index 9eba5b452..a4af523cf 100644
--- a/source/ItemGrid.h
+++ b/source/ItemGrid.h
@@ -72,7 +72,7 @@ public:
 	void Clear(void);
 	
 	/// Returns number of items out of a_ItemStack that can fit in the storage
-	int HowManyCanFit(const cItem & a_ItemStack);
+	int HowManyCanFit(const cItem & a_ItemStack, bool a_AllowNewStacks = true);
 	
 	/** Adds as many items out of a_ItemStack as can fit.
 	If a_AllowNewStacks is set to false, only existing stacks can be topped up;