diff --git a/site/docs/build/index.md b/site/docs/build/index.md
index ad3a168..adf5ea1 100644
--- a/site/docs/build/index.md
+++ b/site/docs/build/index.md
@@ -59,7 +59,7 @@ Environmental variables
 Please read about environmental variables in [the build
 instructions](../maintain/), before running lbmk. You should set
 your variables accordingly, though you do not technically need to; some
-of them may be useful, e.g. `LBMK_THREADS` (sets the number of build threads).
+of them may be useful, e.g. `XBMK_THREADS` (sets the number of build threads).
 
 Sources
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