Can not identify taglib descriptor when it's in jar file.

When I take taglib.tld to /WEB-INF/ directory, it can identify. but when I make the jar and put taglib.tld into /META-INF/ directory which is in jar file, it can not identify, but tomcat can. Is it a bug?

Resource: http://www-900.ibm.com/developerWorks/cn/java/j-jsp09023/index_eng.shtml