diff --git a/commit-reach.c b/commit-reach.c
index efd5925cbb..50175b159e 100644
--- a/commit-reach.c
+++ b/commit-reach.c
@@ -321,7 +321,7 @@ int repo_in_merge_bases_many(struct repository *r, struct commit *commit,
 {
 	struct commit_list *bases;
 	int ret = 0, i;
-	uint32_t generation, min_generation = GENERATION_NUMBER_INFINITY;
+	uint32_t generation, max_generation = GENERATION_NUMBER_ZERO;
 
 	if (repo_parse_commit(r, commit))
 		return ret;
@@ -330,12 +330,12 @@ int repo_in_merge_bases_many(struct repository *r, struct commit *commit,
 			return ret;
 
 		generation = commit_graph_generation(reference[i]);
-		if (generation < min_generation)
-			min_generation = generation;
+		if (generation > max_generation)
+			max_generation = generation;
 	}
 
 	generation = commit_graph_generation(commit);
-	if (generation > min_generation)
+	if (generation > max_generation)
 		return ret;
 
 	bases = paint_down_to_common(r, commit,
diff --git a/t/helper/test-reach.c b/t/helper/test-reach.c
index 14a3655442..cda804ed79 100644
--- a/t/helper/test-reach.c
+++ b/t/helper/test-reach.c
@@ -107,6 +107,8 @@ int cmd__reach(int ac, const char **av)
 		printf("%s(A,B):%d\n", av[1], ref_newer(&oid_A, &oid_B));
 	else if (!strcmp(av[1], "in_merge_bases"))
 		printf("%s(A,B):%d\n", av[1], in_merge_bases(A, B));
+	else if (!strcmp(av[1], "in_merge_bases_many"))
+		printf("%s(A,X):%d\n", av[1], in_merge_bases_many(A, X_nr, X_array));
 	else if (!strcmp(av[1], "is_descendant_of"))
 		printf("%s(A,X):%d\n", av[1], repo_is_descendant_of(r, A, X));
 	else if (!strcmp(av[1], "get_merge_bases_many")) {
diff --git a/t/t6600-test-reach.sh b/t/t6600-test-reach.sh
index 475564bee7..f807276337 100755
--- a/t/t6600-test-reach.sh
+++ b/t/t6600-test-reach.sh
@@ -110,6 +110,36 @@ test_expect_success 'in_merge_bases:miss' '
 	test_three_modes in_merge_bases
 '
 
+test_expect_success 'in_merge_bases_many:hit' '
+	cat >input <<-\EOF &&
+	A:commit-6-8
+	X:commit-6-9
+	X:commit-5-7
+	EOF
+	echo "in_merge_bases_many(A,X):1" >expect &&
+	test_three_modes in_merge_bases_many
+'
+
+test_expect_success 'in_merge_bases_many:miss' '
+	cat >input <<-\EOF &&
+	A:commit-6-8
+	X:commit-7-7
+	X:commit-8-6
+	EOF
+	echo "in_merge_bases_many(A,X):0" >expect &&
+	test_three_modes in_merge_bases_many
+'
+
+test_expect_success 'in_merge_bases_many:miss-heuristic' '
+	cat >input <<-\EOF &&
+	A:commit-6-8
+	X:commit-7-5
+	X:commit-6-6
+	EOF
+	echo "in_merge_bases_many(A,X):0" >expect &&
+	test_three_modes in_merge_bases_many
+'
+
 test_expect_success 'is_descendant_of:hit' '
 	cat >input <<-\EOF &&
 	A:commit-5-7