diff --git a/pkgs/pow-captcha/src/solver-shared.ts b/pkgs/pow-captcha/src/solver-shared.ts
new file mode 100644
index 0000000..95e0577
--- /dev/null
+++ b/pkgs/pow-captcha/src/solver-shared.ts
@@ -0,0 +1,12 @@
+export const WORKER_READY = "fa7c33c3-85cb-4bcd-bffb-59a55d8dda31";
+
+export type Challenge = readonly [Uint8Array, Uint8Array];
+
+export type WorkerRequest = {
+	engine?: undefined | "js" | "wasm";
+	challenges: ReadonlyArray<Challenge>;
+};
+
+export type WorkerResponse = {
+	solutions: ReadonlyArray<Uint8Array>;
+};
diff --git a/pkgs/pow-captcha/src/solver-worker.ts b/pkgs/pow-captcha/src/solver-worker.ts
index 0173635..c414c12 100644
--- a/pkgs/pow-captcha/src/solver-worker.ts
+++ b/pkgs/pow-captcha/src/solver-worker.ts
@@ -1,24 +1,10 @@
 import * as solver from "./solver";
-// import * as wasm from "@pow-captcha/solver-wasm";
-
-export type Challenge = readonly [Uint8Array, Uint8Array];
-
-export type WorkerRequest = {
-	engine?: undefined | "js" | "wasm";
-	challenges: ReadonlyArray<Challenge>;
-};
-
-export type WorkerResponse = {
-	solutions: ReadonlyArray<Uint8Array>;
-};
-
-async function solveWasm(
-	nonce: Uint8Array,
-	target: Uint8Array,
-): Promise<Uint8Array> {
-	const wasm = await import("@pow-captcha/solver-wasm");
-	return wasm.solve(nonce, target);
-}
+import * as wasm from "@pow-captcha/solver-wasm";
+import {
+	WORKER_READY,
+	type WorkerRequest,
+	type WorkerResponse,
+} from "./solver-shared";
 
 async function solve(
 	nonce: Uint8Array,
@@ -30,11 +16,11 @@ async function solve(
 			return await solver.solveJs(nonce, target);
 
 		case "wasm":
-			return await solveWasm(nonce, target);
+			return wasm.solve(nonce, target);
 
 		case undefined:
 			try {
-				return await solveWasm(nonce, target);
+				return wasm.solve(nonce, target);
 			} catch (err) {
 				console.warn(
 					"pow-captcha: Falling back to js solver. Error: ",
@@ -70,3 +56,6 @@ onmessage = (m: MessageEvent<WorkerRequest>) => {
 		console.error("pow-captcha: Failure in worker: ", err);
 	});
 };
+
+// send worker ready
+postMessage(WORKER_READY);
diff --git a/pkgs/pow-captcha/src/solver.ts b/pkgs/pow-captcha/src/solver.ts
index f93deec..5f17507 100644
--- a/pkgs/pow-captcha/src/solver.ts
+++ b/pkgs/pow-captcha/src/solver.ts
@@ -1,4 +1,8 @@
-import type { WorkerRequest, WorkerResponse } from "./solver-worker";
+import {
+	WORKER_READY,
+	type WorkerRequest,
+	type WorkerResponse,
+} from "./solver-shared";
 import { arrayStartsWith, chunkArray } from "./utils";
 
 export async function solveJs(
@@ -51,6 +55,22 @@ export async function solveChallenges(
 		);
 
 		try {
+			// await worker ready
+			await new Promise<void>((onOk, onErr) => {
+				worker.onerror = onErr;
+				worker.onmessage = (m) => {
+					if (m.data !== WORKER_READY) {
+						onErr(
+							new Error(
+								`pow-captcha: Worker-ready ("${WORKER_READY}") expected, got: "${m.data}"`,
+							),
+						);
+					} else {
+						onOk();
+					}
+				};
+			});
+
 			const resultPromise = new Promise<ReadonlyArray<Uint8Array>>(
 				(onOk, onErr) => {
 					worker.onerror = onErr;