diff --git a/SlowBots.md b/SlowBots.md
index 196fd4bd..fb774a2d 100644
--- a/SlowBots.md
+++ b/SlowBots.md
@@ -23,7 +23,9 @@ TRY=ppc64le, freebsd, netbsd-386, ios, linux-arm64-packet
 * `specific-builder-name` (you specify it explicitly by its exact name; see the full list at https://farmer.golang.org/builders)
 * `ios` (alias for `darwin-arm64`)
 
-We might add more aliases later.
+For the main Go repository, the terms after `TRY=` can also be:
+
+* `x/repo` (where `repo` is one of the golang.org/x repositories whose tests should be executed)
 
 When running TryBots again later, the most recent `TRY=` comment on the current patchset is used. To turn it off set `TRY=` with an empty string after the equals sign. If the current patchset doesn't have a `TRY=` comment, the most recent non-empty `TRY=` comment is used.
 
@@ -40,4 +42,6 @@ When running TryBots again later, the most recent `TRY=` comment on the current
 
 ## TODO
 
-Yes, the usability of SlowBots isn't great yet. It was added where it was most convenient. It needs to report things better, make it easier to configure (both CLI and probably a web GUI picker UI), and support restarting things, or modifying in-progress TryBot runs to change the set of builders. Feedback welcome at [golang.org/issue/34501](https://golang.org/issue/34501).
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+- Allow selecting a builder other than `linux-amd64` for x/REPO queries ([golang.org/issue/39201](https://golang.org/issue/39201)).
+
+The usability of SlowBots will be improved over time. It needs to report things better, make it easier to configure (both CLI and probably a web GUI picker UI), and support restarting things, or modifying in-progress TryBot runs to change the set of builders. Feedback welcome at [golang.org/issue/34501](https://golang.org/issue/34501).
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