diff --git a/packages/pg-protocol/src/outbound-serializer.test.ts b/packages/pg-protocol/src/outbound-serializer.test.ts
index aac0c57ba..9337c0471 100644
--- a/packages/pg-protocol/src/outbound-serializer.test.ts
+++ b/packages/pg-protocol/src/outbound-serializer.test.ts
@@ -1,4 +1,6 @@
 import assert from 'assert'
+import fs from 'fs'
+import path from 'path'
 import { serialize } from './serializer'
 import BufferList from './testing/buffer-list'
 
@@ -24,6 +26,12 @@ describe('serializer', () => {
     )
   })
 
+  it('emits declarations that do not need a generic Buffer', function () {
+    // older @types/node releases declare a non-generic Buffer; see #3699
+    const declarations = fs.readFileSync(path.join(__dirname, 'serializer.d.ts'), 'utf8')
+    assert.ok(!declarations.includes('Buffer<'), declarations)
+  })
+
   it('builds password message', function () {
     const actual = serialize.password('!')
     assert.deepEqual(actual, new BufferList().addCString('!').join(true, 'p'))
diff --git a/packages/pg-protocol/src/serializer.ts b/packages/pg-protocol/src/serializer.ts
index bbd59623e..651c4bffa 100644
--- a/packages/pg-protocol/src/serializer.ts
+++ b/packages/pg-protocol/src/serializer.ts
@@ -274,11 +274,11 @@ const serialize = {
   execute,
   describe,
   close,
-  flush: () => flushBuffer,
-  sync: () => syncBuffer,
-  end: () => endBuffer,
+  flush: (): Buffer => flushBuffer,
+  sync: (): Buffer => syncBuffer,
+  end: (): Buffer => endBuffer,
   copyData,
-  copyDone: () => copyDoneBuffer,
+  copyDone: (): Buffer => copyDoneBuffer,
   copyFail,
   cancel,
 }