Use a custom TMP path

Is it possible to configure rclone to use a custom TMP path? I’m running rclone on my NAS, and the amount of RAM limits my TMP directory. Sometimes I see errors in the rclone log:
2017/09/15 09:31:42 ERROR : xxxxxx.mp4: Failed to copy: write /tmp/rclone-b2-xxxxxxxx: no space left on device
Doesn’t seem to be file size dependent.