diff --git a/t/README b/t/README
index 1ae941f88e..b1a598ae39 100644
--- a/t/README
+++ b/t/README
@@ -383,6 +383,10 @@ GIT_TEST_REBASE_USE_BUILTIN=<boolean>, when false, disables the
 builtin version of git-rebase. See 'rebase.useBuiltin' in
 git-config(1).
 
+GIT_TEST_STASH_USE_BUILTIN=<boolean>, when false, disables the
+built-in version of git-stash. See 'stash.useBuiltin' in
+git-config(1).
+
 GIT_TEST_ADD_I_USE_BUILTIN=<boolean>, when true, enables the
 builtin version of git add -i. See 'add.interactive.useBuiltin' in
 git-config(1).