diff --git a/ecma2020regex.cf b/ecma2020regex.cf
index 972a143..6401c93 100644
--- a/ecma2020regex.cf
+++ b/ecma2020regex.cf
@@ -183,11 +183,12 @@ ControlLetterX.          ControlLetter      ::= "X";
 ControlLetterY.          ControlLetter      ::= "Y";
 ControlLetterZ.          ControlLetter      ::= "Z";
 
-token SpecialNormalChar  (char - ["@<>=-^$/\\.,:*+?!()[]{}|0123456789a-zA-Z"]);
+token SpecialNormalChar  (char - ["@<>=-^$/\\.,:*+?!()[]{}|_0123456789a-zA-Z"]);
 
 ControlLetterNormalChar. NormalChar         ::= ControlLetter;
 SpecialLetterNormalChar. NormalChar         ::= SpecialNormalChar;
 ExtraLetterNormalChar.   NormalChar         ::= ExtraNormalChar;
+UnderscoreNormalChar.    NormalChar         ::= "_";
 
 NormalChar1.             ExtraNormalChar    ::= ",";
 NormalChar2.             ExtraNormalChar    ::= "<";
diff --git a/target/ecma2020-regex-parser-0.6.jar b/target/ecma2020-regex-parser-0.6.jar
index 92c82e3..e453e2b 100644
Binary files a/target/ecma2020-regex-parser-0.6.jar and b/target/ecma2020-regex-parser-0.6.jar differ