diff --git a/packages/peer/src/validators.test.ts b/packages/peer/src/validators.test.ts
index ce37a33..c3af6c9 100644
--- a/packages/peer/src/validators.test.ts
+++ b/packages/peer/src/validators.test.ts
@@ -254,6 +254,15 @@ describe('isClientPeerSendMessage', () => {
   ])('rejects %s', (_, overrides) => {
     expect(isClientPeerSendMessage(base(overrides))).toBe(false)
   })
+
+  it.each([
+    ['non-string id', base({ id: 123 as any, kind: 'request', json: { url: '/path' } })],
+    ['binary as string', base({ kind: 'octet-stream', json: {}, binary: 'data' as any })],
+    ['null', null],
+    ['array', []],
+  ])('rejects %s, which is not a peer message', (_, v) => {
+    expect(isClientPeerSendMessage(v)).toBe(false)
+  })
 })
 
 describe('isServerPeerSendMessage', () => {
@@ -270,4 +279,13 @@ describe('isServerPeerSendMessage', () => {
   it('rejects request', () => {
     expect(isServerPeerSendMessage(base({ kind: 'request', json: { url: '/path' } }))).toBe(false)
   })
+
+  it.each([
+    ['non-string id', base({ id: 123 as any, kind: 'response', json: {} })],
+    ['binary as string', base({ kind: 'response', json: {}, binary: 'data' as any })],
+    ['null', null],
+    ['array', []],
+  ])('rejects %s, which is not a peer message', (_, v) => {
+    expect(isServerPeerSendMessage(v)).toBe(false)
+  })
 })
diff --git a/packages/peer/src/validators.ts b/packages/peer/src/validators.ts
index 778b0eb..96874d8 100644
--- a/packages/peer/src/validators.ts
+++ b/packages/peer/src/validators.ts
@@ -137,21 +137,23 @@ export function isPeerStreamCancelMessage(maybe: PeerMessage): maybe is PeerStre
   return maybe.kind === 'stream/cancel' && maybe.json === undefined && maybe.binary === undefined
 }
 
-export function isClientPeerSendMessage(maybe: PeerMessage): maybe is ClientPeerSendMessage {
+export function isClientPeerSendMessage(maybe: unknown): maybe is ClientPeerSendMessage {
   return (
-    isPeerRequestMessage(maybe) ||
-    isPeerCancelMessage(maybe) ||
-    isPeerEventStreamMessage(maybe) ||
-    isPeerOctetStreamMessage(maybe)
+    isPeerMessage(maybe) &&
+    (isPeerRequestMessage(maybe) ||
+      isPeerCancelMessage(maybe) ||
+      isPeerEventStreamMessage(maybe) ||
+      isPeerOctetStreamMessage(maybe))
   )
 }
 
-export function isServerPeerSendMessage(maybe: PeerMessage): maybe is ServerPeerSendMessage {
+export function isServerPeerSendMessage(maybe: unknown): maybe is ServerPeerSendMessage {
   return (
-    isPeerResponseMessage(maybe) ||
-    isPeerCancelMessage(maybe) ||
-    isPeerEventStreamMessage(maybe) ||
-    isPeerOctetStreamMessage(maybe) ||
-    isPeerStreamCancelMessage(maybe)
+    isPeerMessage(maybe) &&
+    (isPeerResponseMessage(maybe) ||
+      isPeerCancelMessage(maybe) ||
+      isPeerEventStreamMessage(maybe) ||
+      isPeerOctetStreamMessage(maybe) ||
+      isPeerStreamCancelMessage(maybe))
   )
 }