diff --git a/src/inventory.cpp b/src/inventory.cpp
index f4a87bec1..1f55c5305 100644
--- a/src/inventory.cpp
+++ b/src/inventory.cpp
@@ -562,7 +562,7 @@ InventoryList & InventoryList::operator = (const InventoryList &other)
 	return *this;
 }
 
-bool InventoryList::operator == (const InventoryList &other)
+bool InventoryList::operator == (const InventoryList &other) const
 {
 	if(m_size != other.m_size)
 		return false;
@@ -875,7 +875,7 @@ Inventory & Inventory::operator = (const Inventory &other)
 	return *this;
 }
 
-bool Inventory::operator == (const Inventory &other)
+bool Inventory::operator == (const Inventory &other) const
 {
 	if(m_lists.size() != other.m_lists.size())
 		return false;
diff --git a/src/inventory.h b/src/inventory.h
index cd592a17a..52b776db3 100644
--- a/src/inventory.h
+++ b/src/inventory.h
@@ -182,7 +182,11 @@ public:
 
 	InventoryList(const InventoryList &other);
 	InventoryList & operator = (const InventoryList &other);
-	bool operator == (const InventoryList &other);
+	bool operator == (const InventoryList &other) const;
+	bool operator != (const InventoryList &other) const
+	{
+		return !(*this == other);
+	}
 
 	const std::string &getName() const;
 	u32 getSize() const;
@@ -258,8 +262,12 @@ public:
 	Inventory(IItemDefManager *itemdef);
 	Inventory(const Inventory &other);
 	Inventory & operator = (const Inventory &other);
-	bool operator == (const Inventory &other);
-	
+	bool operator == (const Inventory &other) const;
+	bool operator != (const Inventory &other) const
+	{
+		return !(*this == other);
+	}
+
 	void serialize(std::ostream &os) const;
 	void deSerialize(std::istream &is);