diff --git a/dist/fuse-worker.cjs b/dist/fuse-worker.cjs
index 05f6f32f6..455bf7543 100644
--- a/dist/fuse-worker.cjs
+++ b/dist/fuse-worker.cjs
@@ -12,6 +12,12 @@ Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' });
 const FUSE_WORKER_UNSUPPORTED_FN_OPTION = (option) => `FuseWorker does not support function-valued option '${option}': functions cannot be transferred to Web Workers via postMessage. Remove this option or fall back to Fuse.`;
 const FUSE_WORKER_TOKEN_SEARCH_UNSUPPORTED = "FuseWorker does not support useTokenSearch: token search depends on corpus-level statistics (df, fieldCount) that are computed per shard, so per-shard scores would diverge from single-thread Fuse. Use Fuse on the main thread for token search.";
 
+//#endregion
+//#region src/helpers/typeGuards.ts
+function isDefined(value) {
+	return value !== void 0 && value !== null;
+}
+
 //#endregion
 //#region src/workers/FuseWorker.ts
 const DEFAULT_MAX_WORKERS = 8;
@@ -159,6 +165,7 @@ var FuseWorker = class FuseWorker {
 		return merged;
 	}
 	async add(doc) {
+		if (!isDefined(doc)) return;
 		await this._ensureInit();
 		const shards = this._shards;
 		const shard = shards[this._addCursor % shards.length];
diff --git a/dist/fuse-worker.mjs b/dist/fuse-worker.mjs
index 1a6ddc4ec..31e51968e 100644
--- a/dist/fuse-worker.mjs
+++ b/dist/fuse-worker.mjs
@@ -10,6 +10,12 @@
 const FUSE_WORKER_UNSUPPORTED_FN_OPTION = (option) => `FuseWorker does not support function-valued option '${option}': functions cannot be transferred to Web Workers via postMessage. Remove this option or fall back to Fuse.`;
 const FUSE_WORKER_TOKEN_SEARCH_UNSUPPORTED = "FuseWorker does not support useTokenSearch: token search depends on corpus-level statistics (df, fieldCount) that are computed per shard, so per-shard scores would diverge from single-thread Fuse. Use Fuse on the main thread for token search.";
 
+//#endregion
+//#region src/helpers/typeGuards.ts
+function isDefined(value) {
+	return value !== void 0 && value !== null;
+}
+
 //#endregion
 //#region src/workers/FuseWorker.ts
 const DEFAULT_MAX_WORKERS = 8;
@@ -156,6 +162,7 @@ var FuseWorker = class FuseWorker {
 		return merged;
 	}
 	async add(doc) {
+		if (!isDefined(doc)) return;
 		await this._ensureInit();
 		const shards = this._shards;
 		const shard = shards[this._addCursor % shards.length];
diff --git a/src/workers/FuseWorker.ts b/src/workers/FuseWorker.ts
index 428327eb7..43532eac6 100644
--- a/src/workers/FuseWorker.ts
+++ b/src/workers/FuseWorker.ts
@@ -1,6 +1,7 @@
 /// <reference lib="dom" />
 
 import * as ErrorMsg from '../core/errorMessages'
+import { isDefined } from '../helpers/typeGuards'
 import type {
   IFuseOptions,
   FuseOptionKey,
@@ -278,6 +279,11 @@ export default class FuseWorker<T> {
   }
 
   async add(doc: T): Promise<void> {
+    // Match Fuse.add's no-op before advancing either global or shard indices.
+    if (!isDefined(doc)) {
+      return
+    }
+
     await this._ensureInit()
 
     const shards = this._shards!
diff --git a/test/fuse-worker.test.js b/test/fuse-worker.test.js
index 7d1ddbe6e..09bdbbfff 100644
--- a/test/fuse-worker.test.js
+++ b/test/fuse-worker.test.js
@@ -124,6 +124,51 @@ describe('FuseWorker sharding', () => {
     fw.terminate()
   })
 
+  test.each([null, undefined])(
+    'add(%s) before initialization does not spawn workers',
+    async (doc) => {
+      MockWorker.instances = []
+      const fw = new FuseWorker(['alpha'], {}, { numWorkers: 2 })
+      await fw.add(doc)
+      expect(MockWorker.instances).toHaveLength(0)
+      expect(await fw.search('')).toEqual([{ item: 'alpha', refIndex: 0 }])
+      fw.terminate()
+    }
+  )
+
+  test.each([1, 3])(
+    'nullish additions preserve single-thread results with %s workers',
+    async (numWorkers) => {
+      const docs = ['alpha', 'beta', 'gamma']
+      const options = { includeMatches: true, includeScore: true, threshold: 0 }
+      const fw = new FuseWorker(docs, options, { numWorkers })
+      const fuse = new Fuse(docs.slice(), options)
+      await fw.search('alpha')
+      for (const doc of [null, undefined, 'delta', null, 'epsilon']) {
+        await fw.add(doc)
+        fuse.add(doc)
+      }
+      for (const query of ['', 'delta', 'epsilon', 'alpha']) {
+        expect(await fw.search(query)).toEqual(fuse.search(query))
+      }
+      fw.terminate()
+    }
+  )
+
+  test('falsy but defined additions are not skipped', async () => {
+    const docs = [{ name: 'alpha' }]
+    const options = { keys: ['name'], threshold: 0 }
+    const fw = new FuseWorker(docs, options, { numWorkers: 3 })
+    const fuse = new Fuse(docs.slice(), options)
+    for (const doc of [null, '', 0, false, { name: 'beta' }]) {
+      await fw.add(doc)
+      fuse.add(doc)
+    }
+    expect(await fw.search('')).toEqual(fuse.search(''))
+    expect(await fw.search('beta')).toEqual(fuse.search('beta'))
+    fw.terminate()
+  })
+
   test('interleaved search/add/setCollection keeps refIndex consistent', async () => {
     MockWorker.instances = []
     const initial = Books.slice(0, 4)