diff --git a/DESCRIPTION b/DESCRIPTION
index 8b7ce20..e7a979c 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: gpindex
 Title: Generalized Price and Quantity Indexes
-Version: 0.5.0.9005
+Version: 0.5.0.9006
 Authors@R: c(
     person("Steve", "Martin", role = c("aut", "cre", "cph"), email = "stevemartin041@gmail.com", comment = c(ORCID = "0000-0003-2544-9480"))
     )
diff --git a/R/geks.R b/R/geks.R
index 62abccd..99a4493 100644
--- a/R/geks.R
+++ b/R/geks.R
@@ -61,14 +61,14 @@ geks_matrix <- function(index, p, q, product, n, nper, window, na.rm) {
 #' @param product A factor, or something that can be coerced into one, that
 #' gives the corresponding product identifier for each element in `p` and
 #' `q`.
-#' @param window The length of the rolling window. The default is a window that
-#' encompasses all periods in `period`. Values that are neither integers
-#' nor length 1 are silently truncated to a length 1 integer.
-#' @param n A number giving the length of the index series for each window,
-#' starting from the end of the window. For example, if there are 13 periods in
-#' `window`, setting `n = 1` gives the index for period 13. The
-#' default gives an index for each period in `window`. Values that are
-#' neither integers nor length 1 are silently truncated to a length 1 integer.
+#' @param window A positive integer giving the length of the rolling window.
+#' The default is a window that encompasses all periods in `period`.
+#' Non-integers are truncated towards zero.
+#' @param n A positive integer giving the length of the index series for each
+#' window, starting from the end of the window. For example, if there are 13
+#' periods in `window`, setting `n = 1` gives the index for period 13. The
+#' default gives an index for each period in `window`. Non-integers are
+#' truncated towards zero.
 #' @param na.rm Passed to `f` to control if missing values are removed.
 #'
 #' @returns
@@ -154,9 +154,9 @@ geks <- function(f) {
       return(list())
     }
 
-    window <- as.integer(window[1L])
-    if (window < 2L) {
-      stop("'window' must be greater than or equal to 2")
+    window <- as.integer(window)
+    if (length(window) > 1L || window < 2L) {
+      stop("'window' must be a integer greater than or equal to 2")
     }
     if (window > nper) {
       stop(
@@ -165,9 +165,9 @@ geks <- function(f) {
       )
     }
 
-    n <- as.integer(n[1L])
-    if (n < 1L) {
-      stop("'n' must be greater than or equal to 1")
+    n <- as.integer(n)
+    if (length(n) > 1L || n < 1L) {
+      stop("'n' must be an integer greater than or equal to 1")
     }
     if (n > window - 1L) {
       stop("'n' must be less than or equal to 'window' minus 1")
diff --git a/man/geks.Rd b/man/geks.Rd
index 7da5be6..43d3601 100644
--- a/man/geks.Rd
+++ b/man/geks.Rd
@@ -57,15 +57,15 @@ to agree with \code{\link[=cut.Date]{cut()}}.}
 gives the corresponding product identifier for each element in \code{p} and
 \code{q}.}
 
-\item{window}{The length of the rolling window. The default is a window that
-encompasses all periods in \code{period}. Values that are neither integers
-nor length 1 are silently truncated to a length 1 integer.}
-
-\item{n}{A number giving the length of the index series for each window,
-starting from the end of the window. For example, if there are 13 periods in
-\code{window}, setting \code{n = 1} gives the index for period 13. The
-default gives an index for each period in \code{window}. Values that are
-neither integers nor length 1 are silently truncated to a length 1 integer.}
+\item{window}{A positive integer giving the length of the rolling window.
+The default is a window that encompasses all periods in \code{period}.
+Non-integers are truncated towards zero.}
+
+\item{n}{A positive integer giving the length of the index series for each
+window, starting from the end of the window. For example, if there are 13
+periods in \code{window}, setting \code{n = 1} gives the index for period 13. The
+default gives an index for each period in \code{window}. Non-integers are
+truncated towards zero.}
 
 \item{na.rm}{Passed to \code{f} to control if missing values are removed.}
 }
diff --git a/tests/testthat/test-geks.R b/tests/testthat/test-geks.R
index 546bfb3..e5eb382 100644
--- a/tests/testthat/test-geks.R
+++ b/tests/testthat/test-geks.R
@@ -99,10 +99,10 @@ test_that("geks agrees with IndexNumR", {
       1.28838882562161, 1.34795095779689, 1.40838221049365, 1.46984928172641,
       1.53258374680655, 1.59693277586978, 1.66348762735518, 1.7335492978583)
   )
-  (test <- with(
+  test <- with(
     dat,
     walsh_geks(price, quantity, period, product, 10, 3)
-  ))
+  )
   expect_equal(
     cumprod(
       as.numeric(
@@ -253,10 +253,16 @@ test_that("errors work for geks", {
   expect_error(
     with(dat, tornqvist_geks(price, quantity, period, product, n = 13))
   )
+  expect_error(
+    with(dat, tornqvist_geks(price, quantity, period, product, n = 1:2))
+  )
   expect_error(
     with(dat, tornqvist_geks(price, quantity, period, product, window = 1))
   )
   expect_error(
     with(dat, tornqvist_geks(price, quantity, period, product, window = 14))
   )
+  expect_error(
+    with(dat, tornqvist_geks(price, quantity, period, product, window = 1:2))
+  )
 })