Incorrect parsing of line-height in font shorthand

[ju1ius]

div.main{
  font: 14px/1.2 Arial, sans-serif;
}

PHP Fatal error:  Uncaught exception 'Exception' with message 'Identifier expected, got /1.2 ' in /home/ju1ius/code/php/third-party/PHP-CSS-Parser/CSSParser.php:110
Stack trace:
#0 CSSParser.php(259): CSSParser->parseIdentifier()
#1 CSSParser.php(228): CSSParser->parseValue()
#2 CSSParser.php(216): CSSParser->parseRule()
#3 CSSParser.php(210): CSSParser->parseRuleSet(Object(CSSDeclarationBlock))
#4 CSSParser.php(50): CSSParser->parseSelector()
#5 CSSParser.php(35): CSSParser->parseList(Object(CSSDocument), true)
#6 CSSParser.php(29): CSSParser->parseDocument(Object(CSSDocument))
#7 test.php(17): CSSParser->parse()
#8 {main}
  thrown in CSSParser.php on line 110