Yang-Data-Impl: write and then merge on same list in modification produces incorrect result

mapNodePath is path to some MapNode.

fooMapNode contains one MapEntryNode child with value "foo".
barMapNode contains one MapEntryNode child with value "bar".

modificationTree.write(mapNodePath, fooMapNode);
modificationTree.merge(mapNodePath, barMapNode);

after commiting this modification to a tree and reading on mapNodePath, it contains only one MapEntryNode child with value "bar". Expected result would be for it to contain both "foo" and "bar" MapEntryNodes