diff --git a/modules/Units/Units.R b/modules/Units/Units.R
index 07e175436a66563fb81ec2df9cd2ffd0447c8b75..a143c0a2037684594cd7642149fa039240e4784c 100644
--- a/modules/Units/Units.R
+++ b/modules/Units/Units.R
@@ -22,9 +22,9 @@ Units <- function(recipe, data) {
   } else {
     flux <- recipe$Analysis$Variable$flux
   }
-  orig_units <- list()
+  orig_units <- vector('list', length = length(data))
+  names(orig_units) <- names(var_names)
   for (element in names(var_names)) {
-    orig_units[[element]] <- c()
     for (x in var_names[[element]]) {
       orig_units[[element]] <- c(orig_units[[element]], 
                                  data[[element]]$attrs$Variable$metadata[[x]]$units)
@@ -48,11 +48,12 @@ Units <- function(recipe, data) {
   user_units <- gsub("\\**", "", user_units)
   user_units <- gsub("\\*", "", user_units)
   orig_units <- lapply(orig_units, function(x) {
-                       x <- tolower(x)
-                       x <- gsub(" ", "", x)
-                       x <- gsub("\\**", "", x)
-                       x <- gsub("\\*", "", x)
-                       x <- unlist(ifelse(rep(length(x)==0, length(user_units)), user_units, x)) #when fcst is NULL
+                       if (!is.null(x)) {
+                         x <- tolower(x)
+                         x <- gsub(" ", "", x)
+                         x <- gsub("\\**", "", x)
+                         x <- gsub("\\*", "", x)
+                       }
                        }) 
   ## TODO:
   ## if "/" appears substitute by -1 in at the end of next unit. How to know?
@@ -62,19 +63,24 @@ Units <- function(recipe, data) {
     res <- data
   } else {
     if (recipe$Run$filesystem == 'esarchive' &&
-        !(length(unique(orig_units)) == 1)) {
-      warn(recipe$Run$logger, 
-           paste("The units in", names(orig_units), "are not all equal.",
+        (sum(!sapply(unique(orig_units), is.null)) != 1)) {
+     warn(recipe$Run$logger, 
+           paste("The units in", paste(names(orig_units), collapse = ', '),
+                 "were not all equal and will be uniformized.",
                  "If this is not expected, please contact the ES data team."))
     }
     res <- sapply(1:length(data), function(x) {
-                  if (!all(orig_units[x] == user_units)) {
-                    result <- units_transform(data[x], 
-                                              orig_units = orig_units[[x]],
-                                              user_units = user_units, 
-                                              var_names[[x]], freq = freq,
-                                              flux = flux,
-                                              ncores = ncores)
+                  if (!is.null(data[[x]])) {
+                    if (!all(orig_units[x] == user_units)) {
+                      result <- units_transform(data[x], 
+                                                orig_units = orig_units[[x]],
+                                                user_units = user_units, 
+                                                var_names[[x]], freq = freq,
+                                                flux = flux,
+                                                ncores = ncores)
+                    } else {
+                      result <- data[x]
+                    }
                   } else {
                     result <- data[x]
                   }