diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1e57c578..669ee02a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,9 +13,9 @@ jobs:
     strategy:
       matrix:
         node-version:
-          - '14'
           - '16'
           - '18'
+          - '20'
 
     steps:
     - uses: actions/checkout@v3
@@ -25,7 +25,6 @@ jobs:
         cache: npm
         node-version: ${{ matrix.node-version }}
 
-    - run: npm install -g npm
     - run: npm install -g nyc codecov
     - run: npm ci
     - run: npm run test:cover
@@ -43,7 +42,7 @@ jobs:
       uses: actions/setup-node@v2
       with:
         cache: npm
-        node-version: '16'
+        node-version: '18'
     - run: npm install -g npm
     - run: npm ci
     - run: npm run test:browser -- --browsers ${{ matrix.browser }}
diff --git a/.github/workflows/fuzz.yml b/.github/workflows/fuzz.yml
index 257e9ae4..1225305e 100644
--- a/.github/workflows/fuzz.yml
+++ b/.github/workflows/fuzz.yml
@@ -21,5 +21,7 @@ jobs:
         cache: npm
         node-version: "18"
 
+    # npm@9 may fail with https://github.com/npm/cli/issues/6723
+    - run: npm install -g npm@8
     - run: npm ci
     - run: npm run test:fuzz
diff --git a/src/index.ts b/src/index.ts
index b4765525..4141ad4d 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -8,7 +8,7 @@ export type { EncodeOptions };
 import { decode, decodeMulti } from "./decode";
 export { decode, decodeMulti };
 import type { DecodeOptions } from "./decode";
-export { DecodeOptions };
+export type { DecodeOptions };
 
 import { decodeAsync, decodeArrayStream, decodeMultiStream, decodeStream } from "./decodeAsync";
 export { decodeAsync, decodeArrayStream, decodeMultiStream, decodeStream };
diff --git a/test/CachedKeyDecoder.test.ts b/test/CachedKeyDecoder.test.ts
index eaee6c8e..09f58424 100644
--- a/test/CachedKeyDecoder.test.ts
+++ b/test/CachedKeyDecoder.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { CachedKeyDecoder, KeyDecoder } from "../src/CachedKeyDecoder";
 import { utf8EncodeJs, utf8Count } from "../src/utils/utf8";
 
diff --git a/test/ExtensionCodec.test.ts b/test/ExtensionCodec.test.ts
index 48d41738..21ae8db6 100644
--- a/test/ExtensionCodec.test.ts
+++ b/test/ExtensionCodec.test.ts
@@ -1,5 +1,5 @@
-import assert from "node:assert";
-import util from "node:util";
+import assert from "assert";
+import util from "util";
 import { encode, decode, ExtensionCodec, decodeAsync } from "../src";
 
 describe("ExtensionCodec", () => {
diff --git a/test/bigint64.test.ts b/test/bigint64.test.ts
index 10e2a65f..fabf0f54 100644
--- a/test/bigint64.test.ts
+++ b/test/bigint64.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decode } from "../src";
 
 describe("useBigInt64: true", () => {
diff --git a/test/codec-bigint.test.ts b/test/codec-bigint.test.ts
index 0a9ef27a..4ed6afff 100644
--- a/test/codec-bigint.test.ts
+++ b/test/codec-bigint.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decode, ExtensionCodec, DecodeError } from "../src";
 
 // There's a built-in `useBigInt64: true` option, but a custom codec might be
diff --git a/test/codec-float.test.ts b/test/codec-float.test.ts
index 050c563e..6b55df70 100644
--- a/test/codec-float.test.ts
+++ b/test/codec-float.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { decode } from "../src";
 import * as ieee754 from "ieee754";
 
diff --git a/test/codec-int.test.ts b/test/codec-int.test.ts
index 2d4d6117..486f93b7 100644
--- a/test/codec-int.test.ts
+++ b/test/codec-int.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { setInt64, getInt64, getUint64, setUint64 } from "../src/utils/int";
 
 const INT64SPECS = {
diff --git a/test/codec-timestamp.test.ts b/test/codec-timestamp.test.ts
index a3927a60..de4f707b 100644
--- a/test/codec-timestamp.test.ts
+++ b/test/codec-timestamp.test.ts
@@ -1,5 +1,5 @@
-import assert from "node:assert";
-import util from "node:util";
+import assert from "assert";
+import util from "util";
 import {
   encode,
   decode,
diff --git a/test/decode-blob.test.ts b/test/decode-blob.test.ts
index 11e9a8b4..4c7c536f 100644
--- a/test/decode-blob.test.ts
+++ b/test/decode-blob.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decode, decodeAsync } from "@msgpack/msgpack";
 
 (typeof Blob !== "undefined" ? describe : describe.skip)("Blob", () => {
diff --git a/test/decode-max-length.test.ts b/test/decode-max-length.test.ts
index c7489c87..7ee2e33a 100644
--- a/test/decode-max-length.test.ts
+++ b/test/decode-max-length.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decode, decodeAsync } from "../src";
 import type { DecoderOptions } from "../src";
 
diff --git a/test/decodeArrayStream.test.ts b/test/decodeArrayStream.test.ts
index a06ed993..04861018 100644
--- a/test/decodeArrayStream.test.ts
+++ b/test/decodeArrayStream.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decodeArrayStream } from "../src";
 
 describe("decodeArrayStream", () => {
diff --git a/test/decodeAsync.test.ts b/test/decodeAsync.test.ts
index 473c1675..0e8d9017 100644
--- a/test/decodeAsync.test.ts
+++ b/test/decodeAsync.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decodeAsync } from "../src";
 
 describe("decodeAsync", () => {
diff --git a/test/decodeMulti.test.ts b/test/decodeMulti.test.ts
index 9d4037dc..346d15c1 100644
--- a/test/decodeMulti.test.ts
+++ b/test/decodeMulti.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decodeMulti } from "@msgpack/msgpack";
 
 describe("decodeMulti", () => {
diff --git a/test/decodeMultiStream.test.ts b/test/decodeMultiStream.test.ts
index 9ef379b0..cef9d6e3 100644
--- a/test/decodeMultiStream.test.ts
+++ b/test/decodeMultiStream.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decodeMultiStream } from "@msgpack/msgpack";
 
 describe("decodeStream", () => {
diff --git a/test/edge-cases.test.ts b/test/edge-cases.test.ts
index f434915a..ca4ad511 100644
--- a/test/edge-cases.test.ts
+++ b/test/edge-cases.test.ts
@@ -1,6 +1,6 @@
 // kind of hand-written fuzzing data
 // any errors should not break Encoder/Decoder instance states
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decodeAsync, decode, Encoder, Decoder, decodeMulti, decodeMultiStream } from "../src";
 import { DataViewIndexOutOfBoundsError } from "../src/Decoder";
 
diff --git a/test/encode.test.ts b/test/encode.test.ts
index 71a0799c..d2679d52 100644
--- a/test/encode.test.ts
+++ b/test/encode.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decode } from "@msgpack/msgpack";
 
 describe("encode", () => {
diff --git a/test/msgpack-ext.test.ts b/test/msgpack-ext.test.ts
index fc96f80b..73a536a1 100644
--- a/test/msgpack-ext.test.ts
+++ b/test/msgpack-ext.test.ts
@@ -1,4 +1,4 @@
-import assert from "node:assert";
+import assert from "assert";
 import { encode, decode, ExtData } from "../src";
 
 function seq(n: number) {
diff --git a/test/msgpack-test-suite.test.ts b/test/msgpack-test-suite.test.ts
index 891c62ca..6800973e 100644
--- a/test/msgpack-test-suite.test.ts
+++ b/test/msgpack-test-suite.test.ts
@@ -1,5 +1,5 @@
-import assert from "node:assert";
-import util from "node:util";
+import assert from "assert";
+import util from "util";
 import { Exam } from "msgpack-test-js";
 import { MsgTimestamp } from "msg-timestamp";
 import { encode, decode, ExtensionCodec, EXT_TIMESTAMP, encodeTimeSpecToTimestamp } from "@msgpack/msgpack";
diff --git a/test/prototype-pollution.test.ts b/test/prototype-pollution.test.ts
index f73f3830..bc15b633 100644
--- a/test/prototype-pollution.test.ts
+++ b/test/prototype-pollution.test.ts
@@ -1,4 +1,4 @@
-import { throws } from "node:assert";
+import { throws } from "assert";
 import { encode, decode, DecodeError } from "@msgpack/msgpack";
 
 describe("prototype pollution", () => {
diff --git a/test/readme.test.ts b/test/readme.test.ts
index ea47b112..fea8123b 100644
--- a/test/readme.test.ts
+++ b/test/readme.test.ts
@@ -1,4 +1,4 @@
-import { deepStrictEqual } from "node:assert";
+import { deepStrictEqual } from "assert";
 import { encode, decode } from "@msgpack/msgpack";
 
 describe("README", () => {
diff --git a/test/reuse-instances.test.ts b/test/reuse-instances.test.ts
index 9930d81c..29a0b786 100644
--- a/test/reuse-instances.test.ts
+++ b/test/reuse-instances.test.ts
@@ -1,4 +1,4 @@
-import { deepStrictEqual } from "node:assert";
+import { deepStrictEqual } from "assert";
 import { Encoder, Decoder, decode } from "@msgpack/msgpack";
 
 const createStream = async function* (...args: any) {
diff --git a/test/whatwg-streams.test.ts b/test/whatwg-streams.test.ts
index 86602643..7a83805a 100644
--- a/test/whatwg-streams.test.ts
+++ b/test/whatwg-streams.test.ts
@@ -1,4 +1,4 @@
-import { deepStrictEqual } from "node:assert";
+import { deepStrictEqual } from "assert";
 import { decodeAsync, encode, decodeArrayStream } from "@msgpack/msgpack";
 
 const isReadableStreamConstructorAvailable: boolean = (() => {