diff --git a/lib/core.js b/lib/core.js
index 606b069e..c06343bc 100644
--- a/lib/core.js
+++ b/lib/core.js
@@ -194,7 +194,7 @@ module.exports = class Core {
         }
       }
 
-      const keyPair = opts.keyPair || (opts.key ? null : crypto.keyPair())
+      const keyPair = opts.keyPair || (opts.key || opts.manifest ? null : crypto.keyPair())
 
       const defaultManifest =
         !opts.manifest &&
diff --git a/test/manifest.js b/test/manifest.js
index 0ab7406c..26cf7bca 100644
--- a/test/manifest.js
+++ b/test/manifest.js
@@ -1518,21 +1518,55 @@ test('manifest - persist if manifest is updated', async function (t) {
   }
 })
 
-test('manifest - invalid signature fails', async function (t) {
-  const core = await create(t, { compat: false })
+test('manifest - writable', async function (t) {
+  const keyPair = crypto.keyPair()
+
+  const manifest = Verifier.createManifest({
+    quorum: 1,
+    signers: [
+      {
+        signature: 'ed25519',
+        publicKey: keyPair.publicKey
+      }
+    ]
+  })
 
-  t.ok(core.writable)
+  const key = Verifier.manifestHash(manifest)
+
+  // correct keyPair
+  const writer = await create(t, { compat: false, manifest, keyPair })
+  t.alike(writer.key, key)
+
+  t.ok(writer.keyPair)
+  t.ok(writer.writable)
 
   const signature = b4a.alloc(32)
-  await t.exception(core.append('hello', { signature }))
+  await t.execution(writer.append('hello'))
 
-  t.is(core.length, 0)
+  t.is(writer.length, 1)
 
-  await core.append(['a', 'b'])
+  // no keyPair
+  const reader = await create(t, { compat: false, manifest })
 
-  t.is(core.length, 2)
+  t.alike(reader.key, key)
+
+  t.absent(reader.keyPair)
+  t.absent(reader.writable)
+
+  await t.exception(reader.append('hello'))
+
+  t.is(reader.length, 0)
+
+  // bad keyPair
+  const imposter = await create(t, { compat: false, manifest, keyPair: crypto.keyPair() })
+  t.alike(imposter.key, key)
+
+  t.ok(imposter.keyPair)
+  t.ok(imposter.writable)
+
+  await t.exception(imposter.append('hello'))
 
-  await t.exception(core.truncate(1, { signature }))
+  t.is(imposter.length, 0)
 })
 
 function createMultiManifest(signers, prologue = null) {