diff --git a/README.md b/README.md
index 73a6d116..43d2a121 100644
--- a/README.md
+++ b/README.md
@@ -38,10 +38,12 @@ On macOS, with [Homebrew](https://brew.sh):
 
 ```sh
 brew tap quine/tap https://forge.quinefoundation.com/quine-global/homebrew-tap.git
+brew trust quine/tap
 brew install --cask quintodrome
 ```
 
-The tap URL is required: without one, `brew tap` assumes a GitHub repo. Update
+The tap URL is required: without one, `brew tap` assumes a GitHub repo. Homebrew
+refuses to load casks from a tap you haven't trusted, hence `brew trust`. Update
 with `brew upgrade --cask quintodrome`.
 
 Or download the `.dmg` from the