diff --git a/nip46.test.ts b/nip46.test.ts
new file mode 100644
index 0000000..cfb0fa9
--- /dev/null
+++ b/nip46.test.ts
@@ -0,0 +1,27 @@
+import { test, expect } from 'bun:test'
+
+import { BunkerSigner, createNostrConnectURI } from './nip46.ts'
+import { generateSecretKey, getPublicKey } from './pure.ts'
+
+const clientSecretKey = generateSecretKey()
+const clientPubkey = getPublicKey(clientSecretKey)
+
+test('createNostrConnectURI always includes the secret', () => {
+  const uri = new URL(createNostrConnectURI({ clientPubkey, relays: ['wss://relay.example.com'], secret: 'hunter2' }))
+
+  expect(uri.searchParams.get('secret')).toEqual('hunter2')
+})
+
+test('fromURI rejects a URI without a secret', async () => {
+  const uri = `nostrconnect://${clientPubkey}?relay=wss://relay.example.com`
+
+  // otherwise a bunker replying `{"result": null}` would match `get('secret')`
+  // and become the signer for this client
+  await expect(BunkerSigner.fromURI(clientSecretKey, uri)).rejects.toThrow(/no secret/)
+})
+
+test('fromURI rejects a URI with an empty secret', async () => {
+  const uri = `nostrconnect://${clientPubkey}?relay=wss://relay.example.com&secret=`
+
+  await expect(BunkerSigner.fromURI(clientSecretKey, uri)).rejects.toThrow(/no secret/)
+})
diff --git a/nip46.ts b/nip46.ts
index 664e8ed..5dc3015 100644
--- a/nip46.ts
+++ b/nip46.ts
@@ -192,8 +192,17 @@ export class BunkerSigner implements Signer {
     bunkerParams: BunkerSignerParams = {},
     maxWaitOrAbort: number | AbortSignal = 300_000,
   ): Promise<BunkerSigner> {
-    const signer = new BunkerSigner(clientSecretKey, bunkerParams)
     const uri = new URL(connectionURI)
+
+    // the secret is what tells the bunker we asked for apart from anyone else who
+    // saw the URI on the relay. without it there is nothing to compare the response
+    // against, and any pubkey that answers would be accepted as our signer.
+    const secret = uri.searchParams.get('secret')
+    if (!secret) {
+      throw new Error('nostrconnect:// URI has no secret')
+    }
+
+    const signer = new BunkerSigner(clientSecretKey, bunkerParams)
     const clientPubkey = getPublicKey(clientSecretKey)
 
     return new Promise((resolve, reject) => {
@@ -213,13 +222,13 @@ export class BunkerSigner implements Signer {
 
               const response = JSON.parse(decryptedContent)
 
-              if (response.result === uri.searchParams.get('secret')) {
+              if (response.result === secret) {
                 sub.close()
 
                 signer.bp = {
                   pubkey: event.pubkey,
                   relays: uri.searchParams.getAll('relay'),
-                  secret: uri.searchParams.get('secret'),
+                  secret,
                 }
                 signer.conversationKey = getConversationKey(clientSecretKey, event.pubkey)
                 signer.setupSubscription()