diff --git a/NEWS.md b/NEWS.md
index 10a4869519..34353096e7 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -4,6 +4,8 @@
 
 * Fixed regression where `draw_key_rect()` stopped using `fill` colours 
   (@mitchelloharawild, #6609).
+* Fixed regression where `scale_{x,y}_*()` threw an error when an expression
+  object is set to `labels` argument (@yutannihilation, #6617).
 
 # ggplot2 4.0.0
 
diff --git a/R/utilities.R b/R/utilities.R
index ca06985f26..37000121c0 100644
--- a/R/utilities.R
+++ b/R/utilities.R
@@ -803,7 +803,7 @@ as_unordered_factor <- function(x) {
 size0 <- function(x) {
   if (obj_is_vector(x)) {
     vec_size(x)
-  } else if (is.vector(x)) {
+  } else if (is.vector(x) || is.expression(x)) {
     length(x)
   } else {
     NULL
diff --git a/tests/testthat/test-scales-breaks-labels.R b/tests/testthat/test-scales-breaks-labels.R
index 1aaf798e52..70a7e0ddcb 100644
--- a/tests/testthat/test-scales-breaks-labels.R
+++ b/tests/testthat/test-scales-breaks-labels.R
@@ -16,6 +16,14 @@ test_that("labels don't have to match null breaks", {
   expect_silent(check_breaks_labels(breaks = NULL, labels = 1:2))
 })
 
+test_that("labels accept expressions", {
+  labels <- parse(text = paste0(1:4, "^degree"))
+  sc <- scale_y_continuous(breaks = 1:4, labels = labels, limits = c(1, 3))
+
+  expect_equal(sc$get_breaks(), 1:4)
+  expect_equal(sc$get_labels(), as.list(labels))
+})
+
 test_that("labels don't have extra spaces", {
   labels <- c("a", "abc", "abcdef")