diff --git a/builtin/gc.c b/builtin/gc.c
index 92c6e7b954..17ff68cbd9 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -1130,8 +1130,10 @@ static int dfs_on_ref(const struct reference *ref, void *cb_data)
 		return 0;
 
 	commit = lookup_commit(the_repository, maybe_peeled);
-	if (!commit)
+	if (!commit || commit->object.flags & SEEN)
 		return 0;
+	commit->object.flags |= SEEN;
+
 	if (repo_parse_commit(the_repository, commit) ||
 	    commit_graph_position(commit) != COMMIT_NOT_FROM_GRAPH)
 		return 0;
@@ -1141,7 +1143,7 @@ static int dfs_on_ref(const struct reference *ref, void *cb_data)
 	if (data->num_not_in_graph >= data->limit)
 		return 1;
 
-	commit_list_append(commit, &stack);
+	commit_list_insert(commit, &stack);
 
 	while (!result && stack) {
 		struct commit_list *parent;
@@ -1162,7 +1164,7 @@ static int dfs_on_ref(const struct reference *ref, void *cb_data)
 				break;
 			}
 
-			commit_list_append(parent->item, &stack);
+			commit_list_insert(parent->item, &stack);
 		}
 	}
 
diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index 6b36f52df7..7cc0ce57f8 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -206,6 +206,31 @@ test_expect_success 'commit-graph auto condition' '
 	test_subcommand $COMMIT_GRAPH_WRITE <cg-two-satisfied.txt
 '
 
+test_expect_success 'commit-graph auto condition with merges' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		git config set maintenance.auto false &&
+		test_commit initial &&
+		git switch --create feature &&
+		test_commit feature-1 &&
+		test_commit feature-2 &&
+		git switch - &&
+		test_commit main-1 &&
+		test_commit main-2 &&
+		git merge feature &&
+
+		# We have 6 commits, none of which are covered by a commit
+		# graph. So this must be the boundary at which we start to
+		# perform maintenance.
+		test_must_fail git -c maintenance.commit-graph.auto=7 \
+			maintenance is-needed --auto --task=commit-graph &&
+		git -c maintenance.commit-graph.auto=6 \
+			maintenance is-needed --auto --task=commit-graph
+	)
+'
+
 test_expect_success 'run --task=bogus' '
 	test_must_fail git maintenance run --task=bogus 2>err &&
 	test_grep "is not a valid task" err