floating on a donkey

Put the summary of the bug you're having here

What I expected to happen was...:
i was doing some tests on my test world but then i tried to test a horse and donkey and i thought they were all right

What actually happened was...:
when i finally went to the donkey i got on it and put a saddle and a chest when i realized i press F5 i saw me floating it looks like i was on its head i wasn't flying....

Steps to Reproduce: none
i'm not sure it actually happen by itself i know this is 1.8.1 pre 2 but is there a way to fix it and also thank you for reading this and hope the bug gets fixed