diff --git a/R/create_attributes_table.R b/R/create_attributes_table.R
index ff5b7ae..34d952b 100644
--- a/R/create_attributes_table.R
+++ b/R/create_attributes_table.R
@@ -553,8 +553,8 @@ table_to_r <- function(table) {
     table_colnames <- table$colnames
     out <- do.call(rbind, lapply(table_data, rbind))
 
-    # Change NULL to NA in list
-    out[sapply(out, is.null)] <- NA
+    # Change NULL to empty string in list
+    out[sapply(out, is.null)] <- ""
 
     if (nrow(out) > 1) {
         out <- as.data.frame(apply(out, 2, unlist), stringsAsFactors = FALSE)
@@ -565,6 +565,9 @@ table_to_r <- function(table) {
     }
 
     colnames(out) <- table_colnames
+    # Convert empty strings to missing values
+    out[sapply(out, function(f){(f == '')})] <- NA
+
     out
 }
 
@@ -621,7 +624,7 @@ build_factors <- function(att_table, data) {
         en_data <- lapply(seq_along(en_data), function(i) {
             attributeName <- colnames(en_data)[i]
             code <- unique(en_data[, i])
-            definition <- NA
+            definition <- ""
             out <- data.frame(attributeName, code, definition, stringsAsFactors = FALSE)
             colnames(out) <- c("attributeName", "code", "definition")
             out <- out[!is.na(code),]
diff --git a/R/obsolete_package.R b/R/obsolete_package.R
index c6b8f4b..6337cce 100644
--- a/R/obsolete_package.R
+++ b/R/obsolete_package.R
@@ -7,12 +7,12 @@
 #' [arcticdatautils::publish_update()] should be used.
 #'
 #' @param mn (MNode) The DataONE member node.
-#' @param metadata_obsolete (character) The metadata PID of the old, or broken, version. Any
-#'   metadata PID from the obsolete version chain can be used - sets the PID to the
-#'   end of the version chain.
-#' @param metadata_new (character) The metadata PID of the new version. Any metadata
-#'   PID from the new version chain can be used - sets the PID to the beginning of
-#'   the version chain.
+#' @param metadata_obsolete (character) The metadata PID of the old, or broken, version.
+#' Sets the PID to the beginning of the version chain (the entry at index=1 of the vector
+#' returned by \code{arcticdatautils::get_all_versions}.
+#' @param metadata_new (character) The metadata PID of the new version. Sets the PID to
+#' the end of the version chain (the last item in the vector returned by
+#' \code{arcticdatautils::get_all_versions}).
 #'
 #' @return (logical) `TRUE`/`FALSE`
 #'
diff --git a/man/obsolete_package.Rd b/man/obsolete_package.Rd
index 54df951..2fb47e7 100644
--- a/man/obsolete_package.Rd
+++ b/man/obsolete_package.Rd
@@ -9,13 +9,13 @@ obsolete_package(mn, metadata_obsolete, metadata_new)
 \arguments{
 \item{mn}{(MNode) The DataONE member node.}
 
-\item{metadata_obsolete}{(character) The metadata PID of the old, or broken, version. Any
-metadata PID from the obsolete version chain can be used - sets the PID to the
-end of the version chain.}
+\item{metadata_obsolete}{(character) The metadata PID of the old, or broken, version.
+Sets the PID to the beginning of the version chain (the entry at index=1 of the vector
+returned by \code{arcticdatautils::get_all_versions}.}
 
-\item{metadata_new}{(character) The metadata PID of the new version. Any metadata
-PID from the new version chain can be used - sets the PID to the beginning of
-the version chain.}
+\item{metadata_new}{(character) The metadata PID of the new version. Sets the PID to
+the end of the version chain (the last item in the vector returned by
+\code{arcticdatautils::get_all_versions}).}
 }
 \value{
 (logical) \code{TRUE}/\code{FALSE}