diff --git a/packages/cli/src/commands/spawn.js b/packages/cli/src/commands/spawn.js
index 7708490ecf..868c4560e5 100644
--- a/packages/cli/src/commands/spawn.js
+++ b/packages/cli/src/commands/spawn.js
@@ -6,5 +6,5 @@ import { withEndoParty } from '../context.js';
 
 export const spawn = async ({ petNames, partyNames }) =>
   withEndoParty(partyNames, { os, process }, async ({ party }) =>
-    Promise.all(petNames.map(petName => E(party).makeWorker(petName))),
+    Promise.all(petNames.map(petName => E(party).provideWorker(petName))),
   );
diff --git a/packages/daemon/src/host.js b/packages/daemon/src/host.js
index 93f8f3a90e..82f4a14a71 100644
--- a/packages/daemon/src/host.js
+++ b/packages/daemon/src/host.js
@@ -5,6 +5,7 @@ import { makeIteratorRef } from './reader-ref.js';
 import { assertPetName, petNamePathFrom } from './pet-name.js';
 import { makePetSitter } from './pet-sitter.js';
 import { makeDeferredTasks } from './deferred-tasks.js';
+import { parseFormulaIdentifier } from './formula-identifier.js';
 
 const { quote: q } = assert;
 
@@ -130,7 +131,7 @@ export const makeHostMaker = ({
       if (petName !== undefined) {
         const formulaIdentifier = petStore.identifyLocal(petName);
         if (formulaIdentifier !== undefined) {
-          if (formulaIdentifier.startsWith('guest:')) {
+          if (parseFormulaIdentifier(formulaIdentifier).type !== 'guest') {
             throw new Error(
               `Existing pet name does not designate a guest powers capability: ${q(
                 petName,
@@ -416,20 +417,6 @@ export const makeHostMaker = ({
       return value;
     };
 
-    /**
-     * @param {string} [petName]
-     * @returns {Promise<import('./types.js').EndoWorker>}
-     */
-    const makeWorker = async petName => {
-      // Behold, recursion:
-      const { formulaIdentifier, value } = await incarnateWorker();
-      if (petName !== undefined) {
-        assertPetName(petName);
-        await petStore.write(petName, formulaIdentifier);
-      }
-      return /** @type {import('./types.js').EndoWorker} */ (value);
-    };
-
     /**
      * @param {string} [petName]
      * @param {import('./types.js').MakeHostOrGuestOptions} [opts]
@@ -599,7 +586,6 @@ export const makeHostMaker = ({
       store,
       provideGuest,
       provideHost,
-      makeWorker,
       provideWorker,
       evaluate,
       makeUnconfined,
diff --git a/packages/daemon/src/types.d.ts b/packages/daemon/src/types.d.ts
index d27a3edb6a..c6b02dcbd9 100644
--- a/packages/daemon/src/types.d.ts
+++ b/packages/daemon/src/types.d.ts
@@ -509,7 +509,6 @@ export interface EndoHost extends EndoDirectory {
     opts?: MakeHostOrGuestOptions,
   ): Promise<EndoHost>;
   makeDirectory(petName: string): Promise<EndoDirectory>;
-  makeWorker(petName: string): Promise<EndoWorker>;
   provideWorker(petName: string): Promise<EndoWorker>;
   evaluate(
     workerPetName: string | undefined,
diff --git a/packages/daemon/test/test-endo.js b/packages/daemon/test/test-endo.js
index 05e00f7f2f..4f3290a2cf 100644
--- a/packages/daemon/test/test-endo.js
+++ b/packages/daemon/test/test-endo.js
@@ -96,7 +96,7 @@ test('lifecycle', async t => {
   );
   const bootstrap = getBootstrap();
   const host = E(bootstrap).host();
-  await E(host).makeWorker('worker');
+  await E(host).provideWorker('worker');
   await E(host).cancel('worker');
   cancel(new Error('Cancelled'));
   await closed.catch(() => {});
@@ -121,7 +121,7 @@ test('spawn and evaluate', async t => {
   );
   const bootstrap = getBootstrap();
   const host = E(bootstrap).host();
-  await E(host).makeWorker('w1');
+  await E(host).provideWorker('w1');
   const ten = await E(host).evaluate('w1', '10', [], []);
   t.is(ten, 10);
 
@@ -150,6 +150,31 @@ test('anonymous spawn and evaluate', async t => {
   await stop(locator);
 });
 
+test('cannot spawn worker with existing non-worker name', async t => {
+  const { promise: cancelled, reject: cancel } = makePromiseKit();
+  t.teardown(() => cancel(Error('teardown')));
+  const locator = makeLocator('tmp', 'spawn-eval-name-reuse');
+
+  await stop(locator).catch(() => {});
+  await purge(locator);
+  await start(locator);
+
+  const { getBootstrap } = await makeEndoClient(
+    'client',
+    locator.sockPath,
+    cancelled,
+  );
+  const bootstrap = getBootstrap();
+  const host = E(bootstrap).host();
+  const ten = await E(host).evaluate('MAIN', '10', [], [], 'ten');
+  t.is(ten, 10);
+  await t.throwsAsync(() => E(host).provideWorker('ten'), {
+    message: 'Not a worker "ten"',
+  });
+
+  await stop(locator);
+});
+
 test('persist spawn and evaluation', async t => {
   const { promise: cancelled, reject: cancel } = makePromiseKit();
   t.teardown(() => cancel(Error('teardown')));
@@ -168,7 +193,7 @@ test('persist spawn and evaluation', async t => {
     const bootstrap = getBootstrap();
     const host = E(bootstrap).host();
 
-    await E(host).makeWorker('w1');
+    await E(host).provideWorker('w1');
 
     const ten = await E(host).evaluate('w1', '10', [], [], 'ten');
     t.is(ten, 10);
@@ -261,7 +286,7 @@ test('closure state lost by restart', async t => {
     );
     const bootstrap = getBootstrap();
     const host = E(bootstrap).host();
-    await E(host).makeWorker('w1');
+    await E(host).provideWorker('w1');
 
     await E(host).evaluate(
       'w1',
@@ -364,7 +389,7 @@ test('persist unconfined services and their requests', async t => {
     );
     const bootstrap = getBootstrap();
     const host = E(bootstrap).host();
-    await E(host).makeWorker('user-worker');
+    await E(host).provideWorker('user-worker');
     await E(host).evaluate(
       'user-worker',
       `
@@ -391,13 +416,13 @@ test('persist unconfined services and their requests', async t => {
     );
     const bootstrap = getBootstrap();
     const host = E(bootstrap).host();
-    await E(host).makeWorker('w1');
+    await E(host).provideWorker('w1');
     await E(host).provideGuest('o1');
     const servicePath = path.join(dirname, 'test', 'service.js');
     const serviceLocation = url.pathToFileURL(servicePath).href;
     await E(host).makeUnconfined('w1', serviceLocation, 'o1', 's1');
 
-    await E(host).makeWorker('w2');
+    await E(host).provideWorker('w2');
     const answer = await E(host).evaluate(
       'w2',
       'E(service).ask()',
@@ -449,7 +474,7 @@ test('persist confined services and their requests', async t => {
     );
     const bootstrap = getBootstrap();
     const host = E(bootstrap).host();
-    await E(host).makeWorker('user-worker');
+    await E(host).provideWorker('user-worker');
     await E(host).evaluate(
       'user-worker',
       `
@@ -476,14 +501,14 @@ test('persist confined services and their requests', async t => {
     );
     const bootstrap = getBootstrap();
     const host = E(bootstrap).host();
-    await E(host).makeWorker('w1');
+    await E(host).provideWorker('w1');
     await E(host).provideGuest('o1');
     const servicePath = path.join(dirname, 'test', 'service.js');
     await doMakeBundle(host, servicePath, bundleName =>
       E(host).makeBundle('w1', bundleName, 'o1', 's1'),
     );
 
-    await E(host).makeWorker('w2');
+    await E(host).provideWorker('w2');
     const answer = await E(host).evaluate(
       'w2',
       'E(service).ask()',
@@ -906,7 +931,7 @@ test('make a host', async t => {
   const bootstrap = getBootstrap();
   const host = E(bootstrap).host();
   const host2 = E(host).provideHost('fellow-host');
-  await E(host2).makeWorker('w1');
+  await E(host2).provideWorker('w1');
   const ten = await E(host2).evaluate('w1', '10', [], []);
   t.is(ten, 10);