diff --git a/src/main/java/net/minecraftforge/items/IItemHandler.java b/src/main/java/net/minecraftforge/items/IItemHandler.java
index f9f725ef53..733b65e771 100644
--- a/src/main/java/net/minecraftforge/items/IItemHandler.java
+++ b/src/main/java/net/minecraftforge/items/IItemHandler.java
@@ -37,9 +37,7 @@ public interface IItemHandler
      *
      * The result's stack size may be greater than the itemstacks max size.
      *
-     * If the result is null, then the slot is empty.
-     * If the result is not null but the stack size is zero, then it represents
-     * an empty slot that will only accept* a specific itemstack.
+     * If the result is empty, then the slot is empty.
      *
      * <p/>
      * IMPORTANT: This ItemStack MUST NOT be modified. This method is not for
@@ -49,7 +47,7 @@ public interface IItemHandler
      * SERIOUSLY: DO NOT MODIFY THE RETURNED ITEMSTACK
      *
      * @param slot Slot to query
-     * @return ItemStack in given slot. May be null.
+     * @return ItemStack in given slot. Empty Itemstack if the slot is empty.
      **/
     @Nonnull
     ItemStack getStackInSlot(int slot);
@@ -60,23 +58,25 @@ public interface IItemHandler
      * Note: This behaviour is subtly different from IFluidHandlers.fill()
      *
      * @param slot     Slot to insert into.
-     * @param stack    ItemStack to insert.
+     * @param stack    ItemStack to insert. This must not be modified by the item handler.
      * @param simulate If true, the insertion is only simulated
      * @return The remaining ItemStack that was not inserted (if the entire stack is accepted, then return ItemStack.EMPTY).
      *         May be the same as the input ItemStack if unchanged, otherwise a new ItemStack.
+     *         The returned ItemStack can be safely modified after.
      **/
     @Nonnull
     ItemStack insertItem(int slot, @Nonnull ItemStack stack, boolean simulate);
 
     /**
-     * Extracts an ItemStack from the given slot. The returned value must be null
-     * if nothing is extracted, otherwise it's stack size must not be greater than amount or the
-     * itemstacks getMaxStackSize().
+     * Extracts an ItemStack from the given slot.
+     * The returned value must be empty if nothing is extracted,
+     * otherwise it's stack size must less than than amount and {@link ItemStack#getMaxStackSize()}.
      *
      * @param slot     Slot to extract from.
      * @param amount   Amount to extract (may be greater than the current stacks max limit)
      * @param simulate If true, the extraction is only simulated
-     * @return ItemStack extracted from the slot, must be ItemStack.EMPTY, if nothing can be extracted
+     * @return ItemStack extracted from the slot, must be empty if nothing can be extracted.
+     *         The returned ItemStack can be safely modified after, so item handlers should return a new or copied stack.
      **/
     @Nonnull
     ItemStack extractItem(int slot, int amount, boolean simulate);
diff --git a/src/main/java/net/minecraftforge/items/IItemHandlerModifiable.java b/src/main/java/net/minecraftforge/items/IItemHandlerModifiable.java
index 18c83bf1fd..0df63164db 100644
--- a/src/main/java/net/minecraftforge/items/IItemHandlerModifiable.java
+++ b/src/main/java/net/minecraftforge/items/IItemHandlerModifiable.java
@@ -32,7 +32,7 @@ public interface IItemHandlerModifiable extends IItemHandler
      * is called unexpectedly.
      *
      * @param slot  Slot to modify
-     * @param stack ItemStack to set slot to (may be null)
+     * @param stack ItemStack to set slot to (may be empty).
      * @throws RuntimeException if the handler is called in a way that the handler
      * was not expecting.
      **/