diff --git a/lib/parser.php b/lib/parser.php
index f89fe66..0b71d7b 100644
--- a/lib/parser.php
+++ b/lib/parser.php
@@ -569,7 +569,7 @@ protected function parse_selector_line($line, $level){
 		$len = strlen($line);
 		for($i = 0; $i < $len; $i++ ){
 			$this->switch_string_state($line{$i});
-			if($this->state != 'st' && $line{$i} == '/' && $line{$i+1} == '/'){ // Break on comment
+			if($this->state != 'st' && (isset($line{$i}) && $line{$i} == '/') && (isset($line{$i+1}) && $line{$i+1} == '/') ){ // Break on comment
 				break;
 			}
 			$this->token .= $line{$i};