Modification of the completion step follows a similar pattern. First, the unit-production relation has to be extended to allow for unit-production chains due to null productions. A rule can effectively act as a unit production that links X and if all other nonterminals on the RHS can expand to . Its contribution to the unit production relation will then be
From the resulting revised matrix we compute the closure as usual.
The second modification is another instance of spontaneous dot shifting. When completing a state and moving the dot to get , additional states have to be added, obtained by moving the dot further over any nonterminals in that have non-zero -expansion probability. As in prediction, forward and inner probabilities are multiplied by the corresponding -expansion probabilities.