diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 573ec2b8a5..0ec2021e13 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -98,5 +98,17 @@ test.list <- atime::atime_test_list(
       paste0('useDynLib(', new.Package_))
   },
 
+  # Fixed in: https://github.com/Rdatatable/data.table/pull/5493 (off-branch)
+  # Merged to master in: https://github.com/Rdatatable/data.table/commit/2d1a0575f87cc50e90f64825c30d7a6cb6b05dd7
+  "transform improved in #5493" = atime::atime_test(
+    N = 10^seq(1, 20),
+    setup = {
+      df <- data.frame(x = runif(N))
+      dt <- as.data.table(df)
+    },
+    expr = data.table:::transform.data.table(dt, y = round(x)),
+    Slow = "0895fa247afcf6b38044bd5f56c0d209691ddb31",
+    Fast = "2d1a0575f87cc50e90f64825c30d7a6cb6b05dd7"),
+
   tests=extra.test.list)
 # nolint end: undesirable_operator_linter.