diff --git a/commit-graph.c b/commit-graph.c
index 9abe62bd5a278a..4b7156fd76596a 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1669,7 +1669,7 @@ static void compute_reachable_generation_numbers(
 			struct commit *current = list->item;
 			struct commit_list *parent;
 			int all_parents_computed = 1;
-			uint32_t max_gen = 0;
+			timestamp_t max_gen = 0;
 
 			for (parent = current->parents; parent; parent = parent->next) {
 				repo_parse_commit(info->r, parent->item);
diff --git a/t/t5328-commit-graph-64bit-time.sh b/t/t5328-commit-graph-64bit-time.sh
index d8891e6a922463..bc651b69deeea4 100755
--- a/t/t5328-commit-graph-64bit-time.sh
+++ b/t/t5328-commit-graph-64bit-time.sh
@@ -74,6 +74,15 @@ test_expect_success 'single commit with generation data exceeding UINT32_MAX' '
 	git -C repo-uint32-max commit-graph verify
 '
 
+test_expect_success 'descendant of commit with date exceeding UINT32_MAX' '
+	git init repo-uint32-max-descendant &&
+	test_commit -C repo-uint32-max-descendant \
+		--date "@4294967300 +0000" future-parent &&
+	test_commit -C repo-uint32-max-descendant present-day-child &&
+	git -C repo-uint32-max-descendant commit-graph write --reachable &&
+	git -C repo-uint32-max-descendant commit-graph verify
+'
+
 test_expect_success PERL_TEST_HELPERS 'reader notices out-of-bounds generation overflow' '
 	graph=.git/objects/info/commit-graph &&
 	test_when_finished "rm -rf $graph" &&