diff --git a/versions/3.0.md b/versions/3.0.md
index 928609647e..ae5b5ce446 100644
--- a/versions/3.0.md
+++ b/versions/3.0.md
@@ -2617,7 +2617,7 @@ The following properties are taken directly from the JSON Schema definition and
 - exclusiveMinimum
 - maxLength
 - minLength
-- pattern
+- pattern (This string SHOULD be a valid regular expression, according to the [ECMA 262 regular expression](https://www.ecma-international.org/ecma-262/5.1/#sec-7.8.5) dialect)
 - maxItems
 - minItems
 - uniqueItems