diff --git a/tests/testthat/test-tree_distance.R b/tests/testthat/test-tree_distance.R
index 94a9ea9f..5e5b9f99 100644
--- a/tests/testthat/test-tree_distance.R
+++ b/tests/testthat/test-tree_distance.R
@@ -769,6 +769,7 @@ test_that("Jaccard RF is correctly calculated", {
 })
 
 test_that("RobinsonFoulds() is correctly calculated", {
+  skip_if_not_installed("phangorn")
   RF <- function(tree1, tree2) {
     suppressMessages(phangorn::RF.dist(reorder(tree1, "cladewise"),
                                        reorder(tree2, "cladewise")))