Unexpected result of MicroKernel#getJournal after MicroKernel#merge

There is an unexpected behavior for the following test case:

String branch = mk.branch(head);
branch = mk.commit("/", "+\"branch\": {}", branch, "");
head = mk.commit("/", "+\"head\": {}", head, "");
head = mk.merge(branch, "");
String n = mk.getNodes("/", head, 10, 0, 10, "");
String j = mk.getJournal(first, head, "/");

getNodes returns both nodes ("branch" and "head"), but
getJournal returns +"/head":{}, >"/head":"/branch"