diff --git a/commit-reach.c b/commit-reach.c
index 5df471a313..3d579d8f7f 100644
--- a/commit-reach.c
+++ b/commit-reach.c
@@ -572,7 +572,7 @@ int repo_is_descendant_of(struct repository *r,
 		struct commit_list *from_list = NULL;
 		int result;
 		commit_list_insert(commit, &from_list);
-		result = can_all_from_reach(from_list, with_commit, 0);
+		result = can_all_from_reach(r, from_list, with_commit, 0);
 		commit_list_free(from_list);
 		return result;
 	} else {
@@ -853,7 +853,8 @@ int commit_contains(struct ref_filter *filter, struct commit *commit,
 	return repo_is_descendant_of(the_repository, commit, list);
 }
 
-int can_all_from_reach_with_flag(struct object_array *from,
+int can_all_from_reach_with_flag(struct repository *r,
+				 struct object_array *from,
 				 unsigned int with_flag,
 				 unsigned int assign_flag,
 				 timestamp_t min_commit_date,
@@ -872,8 +873,7 @@ int can_all_from_reach_with_flag(struct object_array *from,
 		if (!from_one || from_one->flags & assign_flag)
 			continue;
 
-		from_one = deref_tag(the_repository, from_one,
-				     "a from object", 0);
+		from_one = deref_tag(r, from_one, "a from object", 0);
 		if (!from_one || from_one->type != OBJ_COMMIT) {
 			/*
 			 * no way to tell if this is reachable by
@@ -886,7 +886,7 @@ int can_all_from_reach_with_flag(struct object_array *from,
 		}
 
 		list[nr_commits] = (struct commit *)from_one;
-		if (repo_parse_commit(the_repository, list[nr_commits]) ||
+		if (repo_parse_commit(r, list[nr_commits]) ||
 		    commit_graph_generation(list[nr_commits]) < min_generation) {
 			result = 0;
 			goto cleanup;
@@ -921,7 +921,7 @@ int can_all_from_reach_with_flag(struct object_array *from,
 				if (!(parent->item->object.flags & assign_flag)) {
 					parent->item->object.flags |= assign_flag;
 
-					if (repo_parse_commit(the_repository, parent->item) ||
+					if (repo_parse_commit(r, parent->item) ||
 					    parent->item->date < min_commit_date ||
 					    commit_graph_generation(parent->item) < min_generation)
 						continue;
@@ -955,8 +955,8 @@ cleanup:
 	return result;
 }
 
-int can_all_from_reach(struct commit_list *from, struct commit_list *to,
-		       int cutoff_by_min_date)
+int can_all_from_reach(struct repository *r, struct commit_list *from,
+		       struct commit_list *to, int cutoff_by_min_date)
 {
 	struct object_array from_objs = OBJECT_ARRAY_INIT;
 	struct commit_list *from_iter = from, *to_iter = to;
@@ -967,7 +967,7 @@ int can_all_from_reach(struct commit_list *from, struct commit_list *to,
 	while (from_iter) {
 		add_object_array(&from_iter->item->object, NULL, &from_objs);
 
-		if (!repo_parse_commit(the_repository, from_iter->item)) {
+		if (!repo_parse_commit(r, from_iter->item)) {
 			timestamp_t generation;
 			if (from_iter->item->date < min_commit_date)
 				min_commit_date = from_iter->item->date;
@@ -981,7 +981,7 @@ int can_all_from_reach(struct commit_list *from, struct commit_list *to,
 	}
 
 	while (to_iter) {
-		if (!repo_parse_commit(the_repository, to_iter->item)) {
+		if (!repo_parse_commit(r, to_iter->item)) {
 			timestamp_t generation;
 			if (to_iter->item->date < min_commit_date)
 				min_commit_date = to_iter->item->date;
@@ -996,7 +996,7 @@ int can_all_from_reach(struct commit_list *from, struct commit_list *to,
 		to_iter = to_iter->next;
 	}
 
-	result = can_all_from_reach_with_flag(&from_objs, PARENT2, PARENT1,
+	result = can_all_from_reach_with_flag(r, &from_objs, PARENT2, PARENT1,
 					      min_commit_date, min_generation);
 
 	while (from) {
diff --git a/commit-reach.h b/commit-reach.h
index 3f3a563d8a..5e2b82655b 100644
--- a/commit-reach.h
+++ b/commit-reach.h
@@ -88,13 +88,14 @@ int commit_contains(struct ref_filter *filter, struct commit *commit,
  * commits with date below 'min_commit_date' or generation below
  * 'min_generation'.
  */
-int can_all_from_reach_with_flag(struct object_array *from,
+int can_all_from_reach_with_flag(struct repository *r,
+				 struct object_array *from,
 				 unsigned int with_flag,
 				 unsigned int assign_flag,
 				 timestamp_t min_commit_date,
 				 timestamp_t min_generation);
-int can_all_from_reach(struct commit_list *from, struct commit_list *to,
-		       int commit_date_cutoff);
+int can_all_from_reach(struct repository *r, struct commit_list *from,
+		       struct commit_list *to, int commit_date_cutoff);
 
 
 /*
diff --git a/fetch-pack.c b/fetch-pack.c
index 120e01f3cf..26dbbdc4f6 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -2330,8 +2330,8 @@ void negotiate_using_fetch(const struct oid_array *negotiation_restrict_tips,
 			die(_("unexpected 'ready' from remote"));
 		else
 			do_check_stateless_delimiter(stateless_rpc, &reader);
-		if (can_all_from_reach_with_flag(&nt_object_array, COMMON,
-						 REACH_SCRATCH, 0,
+		if (can_all_from_reach_with_flag(the_repository, &nt_object_array,
+						 COMMON, REACH_SCRATCH, 0,
 						 min_generation))
 			last_iteration = 1;
 		trace2_region_leave_printf("negotiation", "round",
diff --git a/t/helper/test-reach.c b/t/helper/test-reach.c
index 5d86a96c17..8ea77a782c 100644
--- a/t/helper/test-reach.c
+++ b/t/helper/test-reach.c
@@ -127,7 +127,7 @@ int cmd__reach(int ac, const char **av)
 		print_sorted_commit_ids(list);
 		commit_list_free(list);
 	} else if (!strcmp(av[1], "can_all_from_reach")) {
-		printf("%s(X,Y):%d\n", av[1], can_all_from_reach(X, Y, 1));
+		printf("%s(X,Y):%d\n", av[1], can_all_from_reach(r, X, Y, 1));
 	} else if (!strcmp(av[1], "can_all_from_reach_with_flag")) {
 		struct commit_list *iter = Y;
 
@@ -136,7 +136,8 @@ int cmd__reach(int ac, const char **av)
 			iter = iter->next;
 		}
 
-		printf("%s(X,_,_,0,0):%d\n", av[1], can_all_from_reach_with_flag(&X_obj, 2, 4, 0, 0));
+		printf("%s(X,_,_,0,0):%d\n", av[1],
+		       can_all_from_reach_with_flag(r, &X_obj, 2, 4, 0, 0));
 	} else if (!strcmp(av[1], "commit_contains")) {
 		struct ref_filter filter = REF_FILTER_INIT;
 		struct contains_cache cache;
diff --git a/t/t6437-submodule-merge.sh b/t/t6437-submodule-merge.sh
index a564758f52..afb484b963 100755
--- a/t/t6437-submodule-merge.sh
+++ b/t/t6437-submodule-merge.sh
@@ -517,4 +517,43 @@ test_expect_success 'merging should fail with no merge base' '
 	)
 '
 
+test_expect_success 'setup for commit-graphs in superproject and submodule' '
+	git init commit-graph &&
+	(cd commit-graph &&
+	git init sub &&
+	for i in 1 2 3 4 5 6 7 8 9 10
+	do
+		test_commit -C sub "sub-$i" || return 1
+	done &&
+
+	git -C sub checkout --detach sub-1 &&
+	git add sub &&
+	git commit -m base &&
+
+	# Write the commit-graph of the superproject while it only
+	# contains a single commit. Any commit-graph position of the
+	# submodule is thus out of bounds for the superproject.
+	git commit-graph write --reachable &&
+
+	git checkout -b side &&
+	git -C sub checkout --detach sub-5 &&
+	git add sub &&
+	git commit -m side &&
+
+	git checkout main &&
+	git -C sub checkout --detach sub-10 &&
+	git add sub &&
+	git commit -m main &&
+
+	git -C sub commit-graph write --reachable)
+'
+
+test_expect_success 'merge does not mix up superproject and submodule commit-graphs' '
+	(cd commit-graph &&
+	git merge side &&
+	git rev-parse HEAD:sub >actual &&
+	git -C sub rev-parse sub-10^{commit} >expect &&
+	test_cmp expect actual)
+'
+
 test_done
diff --git a/upload-pack.c b/upload-pack.c
index a52856d869..550fea6763 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -565,9 +565,9 @@ static int ok_to_give_up(struct upload_pack_data *data)
 	if (!data->have_obj.nr)
 		return 0;
 
-	return can_all_from_reach_with_flag(&data->want_obj, THEY_HAVE,
-					    COMMON_KNOWN, data->oldest_have,
-					    min_generation);
+	return can_all_from_reach_with_flag(the_repository, &data->want_obj,
+					    THEY_HAVE, COMMON_KNOWN,
+					    data->oldest_have, min_generation);
 }
 
 static int get_common_commits(struct upload_pack_data *data,