diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index fddfb1347b..ee2f408e6b 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -119,6 +119,22 @@ test.list <- atime::atime_test_list(
       data.table:::setDT(L)
     },
     Slow = "c4a2085e35689a108d67dacb2f8261e4964d7e12", # Parent of the first commit in the PR that fixes the issue (https://github.com/Rdatatable/data.table/commit/7cc4da4c1c8e568f655ab5167922dcdb75953801)
-    Fast = "1872f473b20fdcddc5c1b35d79fe9229cd9a1d15") # Last commit in the PR that fixes the issue (https://github.com/Rdatatable/data.table/pull/5427/commits)
+    Fast = "1872f473b20fdcddc5c1b35d79fe9229cd9a1d15"),# Last commit in the PR that fixes the issue (https://github.com/Rdatatable/data.table/pull/5427/commits)
+
+  #issue reported in: https://github.com/Rdatatable/data.table/issues/5424
+  #Fixed in: https://github.com/Rdatatable/data.table/pull/5463
+   ".N and := regression fixed in #5463" = atime::atime_test(
+     N = 10^seq(1, 4),
+     setup = {
+       set.seed(123L)
+       dt <- data.table(
+         id = seq_len(N),
+         val = rnorm(N))
+       dt
+     },
+     expr = data.table:::`[.data.table`(dt, , .(vs = (sum(val))), by = .(id)),
+     Before = "be2f72e6f5c90622fe72e1c315ca05769a9dc854",
+     Regression = "e793f53466d99f86e70fc2611b708ae8c601a451",
+     Fixed = "58409197426ced4714af842650b0cc3b9e2cb842")
 )
 # nolint end: undesirable_operator_linter.