diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
index 2677cd5faa..4bb56c167a 100755
--- a/t/t5500-fetch-pack.sh
+++ b/t/t5500-fetch-pack.sh
@@ -892,15 +892,20 @@ test_expect_success 'shallow since with commit graph and already-seen commit' '
 	test_commit other &&
 	git commit-graph write --reachable &&
 	git config core.commitGraph true &&
+	oid_algo=$(test_oid algo) &&
+	oid_other=$(git rev-parse other) &&
+	oid_main=$(git rev-parse main) &&
 
-	GIT_PROTOCOL=version=2 git upload-pack . <<-EOF >/dev/null
-	0012command=fetch
-	$(echo "object-format=$(test_oid algo)" | packetize)
-	00010013deepen-since 1
-	$(echo "want $(git rev-parse other)" | packetize)
-	$(echo "have $(git rev-parse main)" | packetize)
+	test-tool pkt-line pack >input <<-EOF &&
+	command=fetch
+	object-format=$oid_algo
+	0001
+	deepen-since 1
+	want $oid_other
+	have $oid_main
 	0000
 	EOF
+	GIT_PROTOCOL=version=2 git upload-pack . <input >/dev/null
 	)
 '