diff --git a/spec/support/becca_mocking.ts b/spec/support/becca_mocking.ts
index 0c65f16b6..495212226 100644
--- a/spec/support/becca_mocking.ts
+++ b/spec/support/becca_mocking.ts
@@ -4,7 +4,7 @@ import BAttribute from "../../src/becca/entities/battribute.js";
 import becca from "../../src/becca/becca.js";
 import randtoken from "rand-token";
 import type SearchResult from "../../src/services/search/search_result.js";
-import type { NoteType } from "../../src/becca/entities/rows.js";
+import type { NoteRow, NoteType } from "../../src/becca/entities/rows.js";
 randtoken.generator({ source: "crypto" });
 
 function findNoteByTitle(searchResults: Array<SearchResult>, title: string): BNote | undefined {
@@ -59,7 +59,7 @@ function id() {
     return randtoken.generate(10);
 }
 
-function note(title: string, extraParams = {}) {
+function note(title: string, extraParams: Partial<NoteRow> = {}) {
     const row = Object.assign(
         {
             noteId: id(),
diff --git a/src/services/tree.spec.ts b/src/services/tree.spec.ts
new file mode 100644
index 000000000..57a13cf0e
--- /dev/null
+++ b/src/services/tree.spec.ts
@@ -0,0 +1,72 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import becca_mocking from "../../spec/support/becca_mocking.js";
+import becca from "../becca/becca.js";
+import BBranch from "../becca/entities/bbranch.js";
+import BNote from "../becca/entities/bnote.js";
+import tree from "./tree.js";
+import cls from "./cls.js";
+
+describe("Tree", () => {
+    let rootNote!: any;
+
+    beforeEach(() => {
+        becca.reset();
+
+        rootNote = new becca_mocking.NoteBuilder(new BNote({
+            noteId: "root",
+            title: "root",
+            type: "text"
+        }))
+        new BBranch({
+            branchId: "none_root",
+            noteId: "root",
+            parentNoteId: "none",
+            notePosition: 10
+        });
+
+        vi.mock("./sql.js", () => {
+            return {
+                default: {
+                    transactional: (cb) => {
+                        cb();
+                    },
+                    execute: (...args) => { },
+                    replace: (...args) => { },
+                    getMap: (...args) => { }
+                }
+            }
+        });
+
+        vi.mock("./sql_init.js", () => {
+            return {
+                dbReady: () => { console.log("Hello world") }
+            }
+        });
+    });
+
+    it("custom sort order is idempotent", () => {
+        rootNote.label("sorted", "order");
+
+        // Add values which have a defined order.
+        for (let i=0; i<=5; i++) {
+            rootNote.child(becca_mocking.note(String(i)).label("order", String(i)));
+        }
+
+        // Add a few values which have no defined order.
+        for (let i=6; i<10; i++) {
+            rootNote.child(becca_mocking.note(String(i)));
+        }
+
+        const expectedOrder = [ '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' ];
+
+        // Sort a few times to ensure that the resulting order is the same.
+        for (let i=0; i<5; i++) {
+            cls.init(() => {
+                tree.sortNotesIfNeeded(rootNote.note.noteId);
+            });
+
+            const order = rootNote.note.children.map((child) => child.title);
+            expect(order).toStrictEqual(expectedOrder);
+        }
+    });
+});
diff --git a/src/services/tree.ts b/src/services/tree.ts
index 64d1279e5..9b695cd69 100644
--- a/src/services/tree.ts
+++ b/src/services/tree.ts
@@ -145,8 +145,8 @@ function sortNotes(parentNoteId: string, customSortBy: string = "title", reverse
                 return compare(bottomBEl, bottomAEl) * (reverse ? -1 : 1);
             }
 
-            const customAEl = fetchValue(a, customSortBy);
-            const customBEl = fetchValue(b, customSortBy);
+            const customAEl = fetchValue(a, customSortBy) ?? fetchValue(a, "title");
+            const customBEl = fetchValue(b, customSortBy) ?? fetchValue(b, "title");
 
             if (customAEl !== customBEl) {
                 return compare(customAEl, customBEl);