Quick question about Master Tempo & BPM with Ableton...

[DJ Axel Lennox]

Hi I love to make remixes/transitions in ableton. One problem i am having is when i move the master bpm tempo envelope at the bottom to adjust the bpm as the song plays, the track that is NOT
warped moves around, thus making my acapella track off sync with certain parts of my instrumental track.
I obviously keep the acapella track in "warp" mode so i can adjust the bpm of the singing. The instrumental i keep un warped because i want it to stay at one constant BPM without the track moving whenever i move the bottom BPM tempo line.
Thanks in advance.