The array is a fundamental data object in most programs. Its key functionality – storage of and access to a set of same-type elements in $O$(1) time per operation – is also widely employed in other more sophisticated data structures. In an extensible array the number of elements in the set is unknown at the time the program is initiated, and the array might continue to grow right through the program’s execution. In this paper we explore the use of extensible arrays in connection with the task of inverted index construction. We develop and test a space-efficient extensible array arrangement that has been previously described but not to our knowledge employed in practice, and show that it adds considerable flexibility to the index construction process while incurring only modest run-time overheads as a result of access indirections.