diff --git a/packages/taler-wallet-cli/src/harness/harness.ts b/packages/taler-wallet-cli/src/harness/harness.ts
index 137027964..eac55281b 100644
--- a/packages/taler-wallet-cli/src/harness/harness.ts
+++ b/packages/taler-wallet-cli/src/harness/harness.ts
@@ -1860,6 +1860,10 @@ function shellWrap(s: string) {
   return "'" + s.replace("\\", "\\\\").replace("'", "\\'") + "'";
 }
 
+export interface WalletCliOpts {
+  cryptoWorkerType?: "sync" | "node-worker-thread";
+}
+
 export class WalletCli {
   private currentTimetravel: Duration | undefined;
   private _client: WalletCoreApiClient;
@@ -1879,6 +1883,7 @@ export class WalletCli {
   constructor(
     private globalTestState: GlobalTestState,
     private name: string = "default",
+    cliOpts: WalletCliOpts = {},
   ) {
     const self = this;
     this._client = {
@@ -1886,12 +1891,15 @@ export class WalletCli {
         logger.info(
           `calling wallet with timetravel arg ${j2s(self.timetravelArg)}`,
         );
+        const cryptoWorkerArg = cliOpts.cryptoWorkerType
+          ? `--crypto-worker=${cliOpts.cryptoWorkerType}`
+          : "";
         const resp = await sh(
           self.globalTestState,
           `wallet-${self.name}`,
           `taler-wallet-cli ${
             self.timetravelArg ?? ""
-          } --no-throttle -LTRACE --skip-defaults --wallet-db '${
+          } ${cryptoWorkerArg} --no-throttle -LTRACE --skip-defaults --wallet-db '${
             self.dbfile
           }' api '${op}' ${shellWrap(JSON.stringify(payload))}`,
         );
diff --git a/packages/taler-wallet-cli/src/index.ts b/packages/taler-wallet-cli/src/index.ts
index f5f863ca3..47a520c83 100644
--- a/packages/taler-wallet-cli/src/index.ts
+++ b/packages/taler-wallet-cli/src/index.ts
@@ -181,6 +181,9 @@ export const walletCli = clk
       setDangerousTimetravel(x / 1000);
     },
   })
+  .maybeOption("cryptoWorker", ["--crypto-worker"], clk.STRING, {
+    help: "Override crypto worker implementation type."
+  })
   .maybeOption("log", ["-L", "--log"], clk.STRING, {
     help: "configure log level (NONE, ..., TRACE)",
     onPresentHandler: (x) => {
@@ -228,6 +231,7 @@ async function withWallet<T>(
     notifyHandler: (n) => {
       logger.info(`wallet notification: ${j2s(n)}`);
     },
+    cryptoWorkerType: walletCliArgs.wallet.cryptoWorker as any,
   });
 
   if (checkEnvFlag("TALER_WALLET_BATCH_WITHDRAWAL")) {
diff --git a/packages/taler-wallet-cli/src/integrationtests/test-wallet-cryptoworker.ts b/packages/taler-wallet-cli/src/integrationtests/test-wallet-cryptoworker.ts
new file mode 100644
index 000000000..fefdab27a
--- /dev/null
+++ b/packages/taler-wallet-cli/src/integrationtests/test-wallet-cryptoworker.ts
@@ -0,0 +1,55 @@
+/*
+ This file is part of GNU Taler
+ (C) 2020 Taler Systems S.A.
+
+ GNU Taler is free software; you can redistribute it and/or modify it under the
+ terms of the GNU General Public License as published by the Free Software
+ Foundation; either version 3, or (at your option) any later version.
+
+ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+/**
+ * Imports.
+ */
+import { j2s } from "@gnu-taler/taler-util";
+import {
+  checkReserve,
+  CryptoDispatcher,
+  depositCoin,
+  downloadExchangeInfo,
+  findDenomOrThrow,
+  NodeHttpLib,
+  refreshCoin,
+  SynchronousCryptoWorkerFactory,
+  TalerError,
+  topupReserveWithDemobank,
+  WalletApiOperation,
+  withdrawCoin,
+} from "@gnu-taler/taler-wallet-core";
+import { GlobalTestState, WalletCli } from "../harness/harness.js";
+import { createSimpleTestkudosEnvironment } from "../harness/helpers.js";
+
+/**
+ * Run test for the different crypto workers.
+ */
+export async function runWalletCryptoWorkerTest(t: GlobalTestState) {
+  const wallet1 = new WalletCli(t, "w1", {
+    cryptoWorkerType: "sync",
+  });
+
+  await wallet1.client.call(WalletApiOperation.CryptoTest, {});
+
+  const wallet2 = new WalletCli(t, "w2", {
+    cryptoWorkerType: "node-worker-thread",
+  });
+
+  await wallet2.client.call(WalletApiOperation.CryptoTest, {});
+}
+
+runWalletCryptoWorkerTest.suites = ["wallet"];
diff --git a/packages/taler-wallet-cli/src/integrationtests/testrunner.ts b/packages/taler-wallet-cli/src/integrationtests/testrunner.ts
index 98e56d6ff..c22689e46 100644
--- a/packages/taler-wallet-cli/src/integrationtests/testrunner.ts
+++ b/packages/taler-wallet-cli/src/integrationtests/testrunner.ts
@@ -93,6 +93,7 @@ import { runTestWithdrawalManualTest } from "./test-withdrawal-manual.js";
 import { runAgeRestrictionsPeerTest } from "./test-age-restrictions-peer.js";
 import { runWalletBalanceTest } from "./test-wallet-balance.js";
 import { runAgeRestrictionsMixedMerchantTest } from "./test-age-restrictions-mixed-merchant.js";
+import { runWalletCryptoWorkerTest } from "./test-wallet-cryptoworker.js";
 
 /**
  * Test runner.
@@ -115,6 +116,7 @@ const allTests: TestMainFunction[] = [
   runBankApiTest,
   runClaimLoopTest,
   runClauseSchnorrTest,
+  runWalletCryptoWorkerTest,
   runDepositTest,
   runDenomUnofferedTest,
   runExchangeManagementTest,
diff --git a/packages/taler-wallet-core/src/crypto/workers/cryptoDispatcher.ts b/packages/taler-wallet-core/src/crypto/workers/cryptoDispatcher.ts
index 85f9acddc..1c0d509e6 100644
--- a/packages/taler-wallet-core/src/crypto/workers/cryptoDispatcher.ts
+++ b/packages/taler-wallet-core/src/crypto/workers/cryptoDispatcher.ts
@@ -15,7 +15,8 @@
  */
 
 /**
- * API to access the Taler crypto worker thread.
+ * API to access the Taler crypto worker.
+ *
  * @author Florian Dold
  */
 
@@ -76,6 +77,10 @@ interface WorkItem {
  */
 const NUM_PRIO = 5;
 
+/**
+ * A crypto worker factory is responsible for creating new
+ * crypto workers on-demand.
+ */
 export interface CryptoWorkerFactory {
   /**
    * Start a new worker.
diff --git a/packages/taler-wallet-core/src/headless/helpers.ts b/packages/taler-wallet-core/src/headless/helpers.ts
index 63967d4ad..2be9be9a1 100644
--- a/packages/taler-wallet-core/src/headless/helpers.ts
+++ b/packages/taler-wallet-core/src/headless/helpers.ts
@@ -61,6 +61,8 @@ export interface DefaultNodeWalletArgs {
    * of the default one.
    */
   httpLib?: HttpRequestLibrary;
+
+  cryptoWorkerType?: "sync" | "node-worker-thread";
 }
 
 /**
@@ -160,10 +162,11 @@ export async function getDefaultNodeWallet2(
   const myDb = await openTalerDatabase(myIdbFactory, myVersionChange);
 
   let workerFactory;
-  if (process.env["TALER_WALLET_SYNC_CRYPTO"]) {
+  const cryptoWorkerType = args.cryptoWorkerType ?? "node-worker-thread";
+  if (cryptoWorkerType === "sync") {
     logger.info("using synchronous crypto worker");
     workerFactory = new SynchronousCryptoWorkerFactory();
-  } else {
+  } else if (cryptoWorkerType === "node-worker-thread") {
     try {
       // Try if we have worker threads available, fails in older node versions.
       const _r = "require";
@@ -177,6 +180,8 @@ export async function getDefaultNodeWallet2(
       );
       workerFactory = new SynchronousCryptoWorkerFactory();
     }
+  } else {
+    throw Error(`unsupported crypto worker type '${cryptoWorkerType}'`);
   }
 
   const timer = new SetTimeoutTimerAPI();
diff --git a/packages/taler-wallet-webextension/src/wxBackend.ts b/packages/taler-wallet-webextension/src/wxBackend.ts
index 68ec15591..8689c92c7 100644
--- a/packages/taler-wallet-webextension/src/wxBackend.ts
+++ b/packages/taler-wallet-webextension/src/wxBackend.ts
@@ -219,6 +219,7 @@ async function reinitWallet(): Promise<void> {
     httpLib = new BrowserHttpLib();
     // We could (should?) use the BrowserCryptoWorkerFactory here,
     // but right now we don't, to have less platform differences.
+    // cryptoWorker = new BrowserCryptoWorkerFactory();
     cryptoWorker = new SynchronousCryptoWorkerFactory();
     timer = new SetTimeoutTimerAPI();
   }