diff --git a/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/FluidStackList.java b/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/FluidStackList.java
index 6d0b48c3f..763854db3 100755
--- a/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/FluidStackList.java
+++ b/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/FluidStackList.java
@@ -101,7 +101,7 @@ public class FluidStackList implements IFluidStackList {
         FluidStackList list = new FluidStackList();
 
         for (FluidStack stack : stacks.values()) {
-            list.add(stack.copy());
+            list.stacks.put(stack.getFluid(), stack.copy());
         }
 
         return list;
diff --git a/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/ItemStackList.java b/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/ItemStackList.java
index 77de4c318..a5f62df9c 100755
--- a/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/ItemStackList.java
+++ b/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/ItemStackList.java
@@ -107,7 +107,7 @@ public class ItemStackList implements IItemStackList {
         ItemStackList list = new ItemStackList();
 
         for (ItemStack stack : stacks.values()) {
-            list.add(stack.copy());
+            list.stacks.put(stack.getItem(), stack.copy());
         }
 
         return list;