diff --git a/Static-filter-syntax.md b/Static-filter-syntax.md
index 2bdbfb7..6f12b00 100644
--- a/Static-filter-syntax.md
+++ b/Static-filter-syntax.md
@@ -1035,6 +1035,7 @@ Valid directives:
 - `?name`: the value of parameter named `name` will be extracted and replace the current URL as the new URL
 - `+https`: the protocol of the current URL will be forced to `https:`<br>
   This directive will succeed only if the protocol of the current URL is either absent or matches `http:` or `https:`
+- `-base64` ([dev build 1.61.1+](https://github.com/gorhill/uBlock/commit/e81e70937f5b6f8f98bdd8e6f71af030486efab8)): decode as a base64-encoded string
 
 The final computed URL must be a valid URL as per [URL API](https://developer.mozilla.org/en-US/docs/Web/API/URL_API), otherwise the filter will be ignored.