Strange behavior of git rev-list --first-parent --ancesty-path

Hello!

Imagine following tree:
A--B--C
 \      /
  D--E
B is parent #1 of C.

git rev-list --first-parent --ancestry-path D..C returns zero commits. This is correct, since one cannot find any commits between D and C traversing tree by first parent. git rev-list --first-parent --ancestry-path E..C returns SHA of C. This is strange, because --ancestry-path should restrict output to commits being both ancestors of C and descendants of E.

Git did not return me any errors or warnings so I'm assuming that --first-parent and --ancestry-path are OK to be used together.

So, is it a git bug or I'm doing smth wrong?