diff --git a/tool/src/org/antlr/v4/parse/ANTLRLexer.g b/tool/src/org/antlr/v4/parse/ANTLRLexer.g
index f97f5fa0b..ff04fa35f 100644
--- a/tool/src/org/antlr/v4/parse/ANTLRLexer.g
+++ b/tool/src/org/antlr/v4/parse/ANTLRLexer.g
@@ -288,8 +288,12 @@ options {k=1;}
 
 fragment
 LEXER_CHAR_SET
-    :   '[' ('\\]'|'\\' ~']'|~('\\'|']'))* ']'
-    ;
+	:	'['
+		(	'\\' .
+		|	~('\\'|']')
+		)*
+		']'
+	;
 
 // --------------
 // Argument specs