表语形容词原则上是不可以后接名词的。I am due six days' leave. 这个句子无疑是正确的，是词典例句。为什么这个表语形容词可以后接名词呢。唯一的理由就是表语形容词后本来搭配的介词在英语的演变中逐渐脱落了，就好比be worth后接名词或动名词，有的词典解释worth为形容词，但用如介词。有的词典干脆直接说worth是个介词。其实worth后本来有一个介词of，后来of 脱落了，形成了表语形容词后接名词的现象。due这个用法就是脱落了后面的介词for。牛津词典把Sb is due something 和 Sb is due for something 放在一起讨论的。此时due的意思等于deserving something, entitled to something. 以下为牛津的释义和例句：

[not before noun] owed something; deserving something

 due something I'm still due 15 days' leave.

 due for something She's due for promotion soon.