new MESA_GLX_DEPTH_BITS env var
diff --git a/docs/envvars.html b/docs/envvars.html
index 7cda0e4..12e44e2 100644
--- a/docs/envvars.html
+++ b/docs/envvars.html
@@ -32,6 +32,7 @@
 <li>MESA_GLX_FX - set to either "fullscreen" for full-screen rendering,
   "window" to render into a window, or "disable" to disable the Glide driver.
 <li>MESA_GLX_FORCE_ALPHA - if set, forces RGB windows to have an alpha channel.
+<li>MESA_GLX_DEPTH_BITS - specifies default number of bits for depth buffer.
 </ul>