diff --git a/docs/Maintainer-Guidelines.md b/docs/Maintainer-Guidelines.md
index cc7392cf4..cfffc1ae1 100644
--- a/docs/Maintainer-Guidelines.md
+++ b/docs/Maintainer-Guidelines.md
@@ -85,6 +85,11 @@ If the formula uses a repository, then the `url` parameter should have a
 tag or revision. `url`s have versions and are stable (not yet
 implemented!).
 
+Don't merge any formula updates with failing `brew test`s. If a `test do` block
+is failing it needs to be fixed. This may involve replacing more involved tests
+with those that are more reliable. This is fine: false positives are better than
+false negatives as we don't want to teach maintainers to merge red PRs.
+
 ## Common “gotchas”
 1.  [Ensure you have set your username and email address
     properly](https://help.github.com/articles/setting-your-email-in-git/)