diff --git a/Resources-Library.md b/Resources-Library.md
index c3ccd62..b233115 100644
--- a/Resources-Library.md
+++ b/Resources-Library.md
@@ -981,6 +981,7 @@ new in [1.49.3b13](https://github.com/gorhill/uBlock/releases/tag/1.49.3b13), up
 - "stack": considered to be implemented in the future, ideally, AdGuard would support its `stack` parameter as a
 vararg, to be discussed,  
 issue to be solved: https://github.com/uBlockOrigin/uBlock-issues/issues/2783
+     - string or regular expression that must match the current function call stack trace, defaults to matching every call; if regular expression is invalid, it will be skipped
 
 Examples:
  - `kompetent.de##+js(set, Object.keys, trueFunc)`