Java - ConcurrentModificationException when adding to a list

I'm trying to add an item to a list of lists. partitions is a LinkedList of lists of Strings. I'm trying to add an item to the begining of one of the partitions in the list of partitions, but I'm getting a ConcurrentModificationException, even though I'm using a copy of the list called partitionsCopy.

Is there any way to do this? All I can find are examples on how to remove items or add items using ListIterator, but I can't add an item at a specific position with ListIterator

int index = 0;
for (List<String<?>> partition : partitions) {
    if (index > 0) {
        partitionsCopy.get( index ).add(0, lastPartition.get(lastPartition.size() - 1));
    }
    lastPartition = partition;
    index++;
}

partitionsCopy looks like this

List<List<String<?>>> partitionsCopy = new LinkedList<List<String<?>>>( );
partitionsCopy.addAll( partitions );

Here's what I came up with from jtahlborn's answer.

  for ( List<String<?>> partition : partitions ) {
    List<String<?>> list = new ArrayList<String<?>>( );
    list.addAll( partition );
    partitionsCopy.add( list );
  }