[amelia] Error in yy %*% unique(na.omit(x.orig[, i])) : non-conformable arguments

Hello, I'm trying to impute a dataset with a variable to indicate cross-sections. When I impute each geographic unit on its own or in aggregate without the cross-section specified, the imputation completes without error. However, when I impute the dataset with the argument cs = "region", I receive the following error: Error in yy %*% unique(na.omit(x.orig[, i])) : non-conformable arguments My code looks as follows: imputed <- amelia(W, m = 1, cs = "region", idvars = c("bunch", "of", "variables"), noms = c("bunch", "more", "variables")) Any help would be greatly appreciated. Thanks, Gregory