diff --git a/docs/envvars.html b/docs/envvars.html
index 06aa0ac9369..e21b7c1aaa0 100644
--- a/docs/envvars.html
+++ b/docs/envvars.html
@@ -163,6 +163,7 @@ See the Xlib software driver page for details.
blorp - emit messages about the blorp operations (blits & clears)
nodualobj - suppress generation of dual-object geometry shader code
optimizer - dump shader assembly to files at each optimization pass and iteration that make progress
+ vec4 - force vec4 mode in vertex shader