diff --git a/R/reformat_GSOD.R b/R/reformat_GSOD.R
index 6c8ea997..bf5d4877 100644
--- a/R/reformat_GSOD.R
+++ b/R/reformat_GSOD.R
@@ -16,12 +16,14 @@
 #' up a parallel backend of your choice, \emph{e.g.},
 #' \code{future::plan("multisession")}.  See Examples for more.
 #'
-#' @param dsn User supplied file path to location of data files on local disk
-#' for tidying.
-#' @param file_list User supplied list of files of data on local disk for
-#' tidying.
+#' @param dsn User supplied full file path to location of data files on local
+#'  disk for tidying.
+#' @param file_list User supplied list of file paths to individual files of data
+#'  on local disk for tidying.  Ignored if \code{dsn} is set.  Use if there are
+#'  other files in the \code{dsn} that you do not wish to reformat.
 #'
 #' @details
+#'
 #' If multiple stations are given, data are summarised for each year by station,
 #' which include vapour pressure and relative humidity elements calculated from
 #' existing data in \acronym{GSOD}.  Else, a single station is tidied and a data
@@ -93,6 +95,13 @@ reformat_GSOD <- function(dsn = NULL, file_list = NULL) {
   load(system.file("extdata", "isd_history.rda", package = "GSODR")) # nocov
   setkeyv(isd_history, "STNID")
 
+  # If both dsn and file_path are set, emit message that only dsn is used
+  if (!is.null(dsn) & !is.null(file_list)) {
+    message("\nYou have specified both `file_list` and `dsn`.\n",
+            "Proceeding with using only the value from `dsn`.\n",
+            "See `?reformat_GSOD` if this behaviour was not expected.\n")
+  }
+
   # If dsn !NULL, create a list of files to reformat
   if (!is.null(dsn)) {
     file_list <- list.files(path = dsn,
diff --git a/man/reformat_GSOD.Rd b/man/reformat_GSOD.Rd
index 02c63236..0bb0b8a6 100644
--- a/man/reformat_GSOD.Rd
+++ b/man/reformat_GSOD.Rd
@@ -7,11 +7,12 @@
 reformat_GSOD(dsn = NULL, file_list = NULL)
 }
 \arguments{
-\item{dsn}{User supplied file path to location of data files on local disk
-for tidying.}
+\item{dsn}{User supplied full file path to location of data files on local
+disk for tidying.}
 
-\item{file_list}{User supplied list of files of data on local disk for
-tidying.}
+\item{file_list}{User supplied list of file paths to individual files of data
+on local disk for tidying.  Ignored if \code{dsn} is set.  Use if there are
+other files in the \code{dsn} that you do not wish to reformat.}
 }
 \value{
 A data frame as a \code{\link[data.table]{data.table}} object of
@@ -35,6 +36,7 @@ up a parallel backend of your choice, \emph{e.g.},
 \code{future::plan("multisession")}.  See Examples for more.
 
 
+
 If multiple stations are given, data are summarised for each year by station,
 which include vapour pressure and relative humidity elements calculated from
 existing data in \acronym{GSOD}.  Else, a single station is tidied and a data
diff --git a/tests/testthat/test-reformat_GSOD.R b/tests/testthat/test-reformat_GSOD.R
index bc0b4712..67af90d9 100644
--- a/tests/testthat/test-reformat_GSOD.R
+++ b/tests/testthat/test-reformat_GSOD.R
@@ -11,7 +11,8 @@ test_that("reformat_GSOD file_list parameter reformats data properly", {
 
   # set up options for curl
 
-  url_base <- "https://www.ncei.noaa.gov/data/global-summary-of-the-day/access/1960/"
+  url_base <-
+    "https://www.ncei.noaa.gov/data/global-summary-of-the-day/access/1960/"
   test_files <-
     c("06600099999.csv", "06620099999.csv")
   destinations <- file.path(tempdir(), test_files)
@@ -45,6 +46,11 @@ test_that("reformat_GSOD file_list parameter reformats data properly", {
   expect_length(x, 44)
   expect_is(x, "data.frame")
 
+  # Check that a message is emitted when both dsn and file_list are set --------
+  expect_message(reformat_GSOD(dsn = tempdir(),
+                               file_list = file_list),
+                 regexp = "\nYou have specified both `file_list` and `dsn`. *")
+
   unlink(destinations)
 })