diff --git a/R/govTable.R b/R/govTable.R
index 58509c5..fdf54bc 100644
--- a/R/govTable.R
+++ b/R/govTable.R
@@ -87,13 +87,16 @@ govTable <- function(inputId, df, caption, caption_size = "l",
   }
 
   #Change width of columns if requested
-  for(i in 1:length(width_overwrite)) {
+  if(!is.null(width_overwrite)){
+    for(i in 1:length(width_overwrite)) {
       gov_table$children[[2]]$children[[1]][[3]][[1]][[i]]$attribs$class <-
         paste0(
           gov_table$children[[2]]$children[[1]][[3]][[1]][[i]]$attribs$class,
           " govuk-!-width-", width_overwrite[i])
+    }
   }
 
+
   return(gov_table)
 }
 
diff --git a/tests/testthat/test-govTable.R b/tests/testthat/test-govTable.R
index d23e5a0..4575ad0 100644
--- a/tests/testthat/test-govTable.R
+++ b/tests/testthat/test-govTable.R
@@ -6,6 +6,7 @@ test_that("table works", {
 
     example_data <- data.frame(Months, Bikes, Cars)
 
+  # test table with specified widths
   table_check <- govTable(
     "tab1", example_data, "Test", "l", num_col = c(2,3),
     width_overwrite = c("one-half", "one-quarter", "one-quarter"))
@@ -25,4 +26,45 @@ test_that("table works", {
     3
   )
 
+# test table with unspecified widths
+  table_check2 <- govTable(
+    "tab2", example_data, "Test", "l", num_col = c(2,3),
+    width_overwrite = NULL)
+
+  expect_identical(
+    table_check2$children[[2]]$children[[1]][[3]][[1]][[1]]$attribs$class,
+    "govuk-table__header"
+  )
+
+  expect_identical(
+    table_check2$children[[2]]$children[[1]][[3]][[1]][[2]]$attribs$class,
+    "govuk-table__header govuk-table__header--numeric"
+  )
+
+  expect_equal(
+    length(table_check2$children[[3]]),
+    3
+  )
+
+
+  # and if the argument isn't mentioned at all
+  table_check3 <- govTable(
+    "tab2", example_data, "Test", "l", num_col = c(2,3))
+
+  expect_identical(
+    table_check3$children[[2]]$children[[1]][[3]][[1]][[1]]$attribs$class,
+    "govuk-table__header"
+  )
+
+  expect_identical(
+    table_check3$children[[2]]$children[[1]][[3]][[1]][[2]]$attribs$class,
+    "govuk-table__header govuk-table__header--numeric"
+  )
+
+  expect_equal(
+    length(table_check3$children[[3]]),
+    3
+  )
+
+
 })