diff --git a/.buildlibrary b/.buildlibrary
index 65e500a..3478888 100644
--- a/.buildlibrary
+++ b/.buildlibrary
@@ -1,4 +1,4 @@
-ValidationKey: '615880016'
+ValidationKey: '615930987'
 AcceptedWarnings:
 - 'Warning: package ''.*'' was built under R version'
 - 'Warning: namespace ''.*'' is not available and has been replaced'
diff --git a/CITATION.cff b/CITATION.cff
index 24db312..77b824c 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -2,8 +2,8 @@ cff-version: 1.2.0
 message: If you use this software, please cite it using the metadata from this file.
 type: software
 title: 'quitte: Bits and pieces of code to use with quitte-style data frames'
-version: 0.3128.2
-date-released: '2023-11-27'
+version: 0.3128.3
+date-released: '2023-11-28'
 abstract: A collection of functions for easily dealing with quitte-style data frames,
   doing multi-model comparisons and plots.
 authors:
diff --git a/DESCRIPTION b/DESCRIPTION
index 73409af..0007df4 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,8 +1,8 @@
 Type: Package
 Package: quitte
 Title: Bits and pieces of code to use with quitte-style data frames
-Version: 0.3128.2
-Date: 2023-11-27
+Version: 0.3128.3
+Date: 2023-11-28
 Authors@R: c(
     person("Michaja", "Pehl", , "pehl@pik-potsdam.de", role = c("aut", "cre")),
     person("Nico", "Bauer", , "nicolasb@pik-potsdam.de", role = "aut"),
diff --git a/R/cartesian.R b/R/cartesian.R
index 627ff13..2026535 100644
--- a/R/cartesian.R
+++ b/R/cartesian.R
@@ -1,4 +1,4 @@
-#' Generate cartesian product from to character vectors
+#' Generate Cartesian product from character vectors
 #'
 #' @param ... objects that can be coerced to character vectors
 #' @param sep a character string that will separate the elements of `...` in the
@@ -14,25 +14,14 @@
 #'
 #' @export
 cartesian <- function(..., sep = '.') {
-    dots <- list(...)
+    if (0 == length(dots <- list(...)))
+        return(NULL)
 
-    L <- lengths(dots)
+    v <- as.character(dots[[1]])
+    for (i in dots[-1])
+        v <- paste(rep(v, each = length(i)),
+                   rep(as.character(i), times = length(v)),
+                   sep = sep)
 
-    apply(
-        X = sapply(
-            X = seq_along(dots),
-            FUN = function(i) {
-                # lengths of dots elements before i (excluding)
-                times_slice <- L[seq_len(i - 1)]
-                # lengths of dot elements after i (excluding)
-                each_slice  <- L[setdiff(seq_along(dots), seq_len(i))]
-
-                rep(rep(dots[[i]], times = prod(times_slice)),
-                    each = prod(each_slice))
-            }
-        ),
-        MARGIN = 1,
-        FUN = paste,
-        collapse = sep
-    )
+    return(v)
 }
diff --git a/README.md b/README.md
index 7b4d8d2..15bc9ff 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # Bits and pieces of code to use with quitte-style data frames
 
-R package **quitte**, version **0.3128.2**
+R package **quitte**, version **0.3128.3**
 
 [![CRAN status](https://www.r-pkg.org/badges/version/quitte)](https://cran.r-project.org/package=quitte)  [![R build status](https://github.com/pik-piam/quitte/workflows/check/badge.svg)](https://github.com/pik-piam/quitte/actions) [![codecov](https://codecov.io/gh/pik-piam/quitte/branch/master/graph/badge.svg)](https://app.codecov.io/gh/pik-piam/quitte) [![r-universe](https://pik-piam.r-universe.dev/badges/quitte)](https://pik-piam.r-universe.dev/builds)
 
@@ -47,7 +47,7 @@ In case of questions / problems please contact Michaja Pehl <michaja.pehl@pik-po
 
 To cite package **quitte** in publications use:
 
-Pehl M, Bauer N, Hilaire J, Levesque A, Luderer G, Schultes A, Dietrich J, Richters O (2023). _quitte: Bits and pieces of code to use with quitte-style data frames_. R package version 0.3128.2, <https://github.com/pik-piam/quitte>.
+Pehl M, Bauer N, Hilaire J, Levesque A, Luderer G, Schultes A, Dietrich J, Richters O (2023). _quitte: Bits and pieces of code to use with quitte-style data frames_. R package version 0.3128.3, <https://github.com/pik-piam/quitte>.
 
 A BibTeX entry for LaTeX users is
 
@@ -56,7 +56,7 @@ A BibTeX entry for LaTeX users is
   title = {quitte: Bits and pieces of code to use with quitte-style data frames},
   author = {Michaja Pehl and Nico Bauer and Jérôme Hilaire and Antoine Levesque and Gunnar Luderer and Anselm Schultes and Jan Philipp Dietrich and Oliver Richters},
   year = {2023},
-  note = {R package version 0.3128.2},
+  note = {R package version 0.3128.3},
   url = {https://github.com/pik-piam/quitte},
 }
 ```
diff --git a/tests/testthat/test-cartesian.R b/tests/testthat/test-cartesian.R
index 6d998bd..52075f1 100644
--- a/tests/testthat/test-cartesian.R
+++ b/tests/testthat/test-cartesian.R
@@ -1,5 +1,5 @@
 test_that(
-    desc = 'cartesian() generates correct combinations',
+    desc = 'cartesian(...) generates correct combinations',
     code = {
         expect_equal(
             object = cartesian(1:2),
@@ -18,3 +18,9 @@ test_that(
                          '2.3.7', '2.3.8', '2.3.9', '2.4.7', '2.4.8', '2.4.9',
                          '2.5.7', '2.5.8', '2.5.9', '2.6.7', '2.6.8', '2.6.9'))
     })
+
+test_that(
+    desc = 'cartesian() returns NULL',
+    code = {
+        expect_null(object = cartesian())
+    })