**MacOS X:** There was an error building the 1.85.3 release on OS X so 1.85.4 is a re-release of 1.85.3 for that platform (so the changelog below reflects the changes from 1.85.2->1.85.4).
**Win32:** there was a bug in pyglet that was preventing us from gamma-correcting monitors (script crashed, so it was very obvious if the problem affected you!). Pyglet has been tweaked in this release but, again, the PsychoPy code itself is unchanged from the code in 1.85.3
**linux:** there is no need to upgrade to 1.85.4 if you already updated to 1.85.3