2 files changed, 2 insertions, 0 deletions
diff --git a/docs/Lexer b/docs/Lexer
index 8f8e1ea..e945f9b 100644
--- a/docs/Lexer
+++ b/docs/Lexer
@@ -10,6 +10,7 @@ First sets
 IDENT 		[a-zA-Z] | '-' | '_' | [^#x0-#x7F] | '\'
 ATKEYWORD	'@'
 STRING		'"' | "'"
+INVALID_STRING	'"' | "'"
 HASH		'#'
 NUMBER		[0-9] | '.'
 PERCENTAGE	[0-9] | '.'
diff --git a/docs/Tokens b/docs/Tokens
index 21e09da..b912f3c 100644
--- a/docs/Tokens
+++ b/docs/Tokens
@@ -28,6 +28,7 @@ Tokens
 IDENT          ::= ident
 ATKEYWORD      ::= '@' ident
 STRING         ::= string
+INVALID_STRING ::= '"' (stringchar | "'")* [^"] | "'" (stringchar | '"')* [^']
 HASH           ::= '#' name
 NUMBER         ::= num
 PERCENTAGE     ::= num '%'