diff --git a/R/data.table.R b/R/data.table.R
index 473cf6e76..801482147 100644
--- a/R/data.table.R
+++ b/R/data.table.R
@@ -882,7 +882,7 @@ replace_dot_alias = function(e) {
           bynames = allbyvars = NULL
           # the rest now fall through
         } else bynames = names(byval)
-        if (is.atomic(byval)) {
+        if (is.atomic(byval) || is.null(byval)) {
           if (is.character(byval) && length(byval)<=ncol(x) && !(is.name(bysub) && bysub %chin% names_x) ) {
             stopf("'by' appears to evaluate to column names but isn't c() or key(). Use by=list(...) if you can. Otherwise, by=eval%s should work. This is for efficiency so data.table can detect which columns are needed.", deparse(bysub))
           } else {
diff --git a/R/frank.R b/R/frank.R
index ba90a83b9..419f5ea41 100644
--- a/R/frank.R
+++ b/R/frank.R
@@ -12,7 +12,7 @@ frankv = function(x, cols=seq_along(x), order=1L, na.last=TRUE, ties.method=c("a
     .Call(Csetlistelt, xx, 1L, x)
     xx
   }
-  if (is.atomic(x)) {
+  if (is.atomic(x) || is.null(x)) {
     if (!missing(cols) && !is.null(cols))
       stopf("x is a single vector, non-NULL 'cols' doesn't make sense")
     cols = 1L
diff --git a/R/fread.R b/R/fread.R
index f8b025d9c..e0337c591 100644
--- a/R/fread.R
+++ b/R/fread.R
@@ -135,7 +135,7 @@ yaml=FALSE, autostart=NA, tmpdir=tempdir(), tz="UTC")
     if (!allNA(colClasses)) stopf("colClasses is type 'logical' which is ok if all NA but it has some TRUE or FALSE values in it which is not allowed. Please consider the drop= or select= argument instead. See ?fread.")
     colClasses = NULL
   }
-  if (!is.null(colClasses) && is.atomic(colClasses)) {
+  if (!is.null(colClasses) && is.atomic(colClasses)) { ## future R can use  if (is.atomic(.))
     if (!is.character(colClasses)) stopf("colClasses is not type list or character vector")
     if (!length(colClasses)) {
       colClasses=NULL;
diff --git a/R/print.data.table.R b/R/print.data.table.R
index 16950fd11..7271ac458 100644
--- a/R/print.data.table.R
+++ b/R/print.data.table.R
@@ -141,7 +141,8 @@ print.data.table = function(x, topn=getOption("datatable.print.topn"),
 }
 
 format.data.table = function (x, ..., justify="none") {
-  if (is.atomic(x) && !is.null(x)) {
+  if (is.atomic(x) && !is.null(x)) { ## future R can use  if (is.atomic(x))
+
     stopf("Internal structure doesn't seem to be a list. Possibly corrupt data.table.")
   }
   do.call("cbind", lapply(x, format_col, ..., justify=justify))
diff --git a/R/setkey.R b/R/setkey.R
index 3bd3f782c..5f3027a2d 100644
--- a/R/setkey.R
+++ b/R/setkey.R
@@ -169,7 +169,7 @@ is.sorted = function(x, by=NULL) {
 ORDERING_TYPES = c('logical', 'integer', 'double', 'complex', 'character')
 forderv = function(x, by=seq_along(x), retGrp=FALSE, sort=TRUE, order=1L, na.last=FALSE)
 {
-  if (is.atomic(x)) {  # including forderv(NULL) which returns error consistent with base::order(NULL),
+  if (is.atomic(x) || is.null(x)) {  # including forderv(NULL) which returns error consistent with base::order(NULL),
     if (!missing(by) && !is.null(by)) stopf("x is a single vector, non-NULL 'by' doesn't make sense")
     by = NULL
   } else {