Systems, methods, and software can be used to disambiguate an input into a handheld electronic device. In some aspect, one computer-implemented method includes detecting an ambiguous input including one or more selections of one or more input keys; generating one or more prefix objects corresponding with the ambiguous input; generating an output set including at least some of the one or more prefix objects, wherein each of the at least some of the one or more prefix objects is associated with an identified corresponding word object; determining, using a processor, a quantity of prefix objects in the output set is fewer than a predetermined quantity, and, based on the determination, adding as an orphan prefix object to the output set an additional prefix object of the one or more of prefix objects for which a corresponding word object was not identified; and outputting the output set.