diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index fbf0d64578..b85d07f60a 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -811,4 +811,31 @@ test_expect_success 'set up and verify repo with generation data overflow chunk'
 
 graph_git_behavior 'generation data overflow chunk repo' repo left right
 
+test_expect_failure 'overflow during generation version upgrade' '
+	git init overflow-v2-upgrade &&
+	(
+		cd overflow-v2-upgrade &&
+
+		# This commit will have a date at two seconds past the Epoch,
+		# and a (v1) generation number of 1, since it is a root commit.
+		#
+		# The offset will then be computed as 1-2, which will underflow
+		# to 2^31, which is greater than the v2 offset small limit of
+		# 2^31-1.
+		#
+		# This is sufficient to need a large offset table for the v2
+		# generation numbers.
+		test_commit --date "@2 +0000" base &&
+		git repack -d &&
+
+		# Test that upgrading from generation v1 to v2 correctly
+		# produces the overflow table.
+		git -c commitGraph.generationVersion=1 commit-graph write &&
+		git -c commitGraph.generationVersion=2 commit-graph write \
+			--changed-paths &&
+
+		git rev-list --all
+	)
+'
+
 test_done