diff --git a/test/parallel/test-fs-promises-file-handle-write.js b/test/parallel/test-fs-promises-file-handle-write.js
index 3c25842d8bf9cc..b558335c9f6c34 100644
--- a/test/parallel/test-fs-promises-file-handle-write.js
+++ b/test/parallel/test-fs-promises-file-handle-write.js
@@ -53,7 +53,12 @@ async function validateNonUint8ArrayWrite() {
 async function validateNonStringValuesWrite() {
   const filePathForHandle = path.resolve(tmpDir, 'tmp-non-string-write.txt');
   const fileHandle = await open(filePathForHandle, 'w+');
-  const nonStringValues = [123, {}, new Map()];
+  const nonStringValues = [
+    123, {}, new Map(),
+    new String('notPrimitive'),
+    { toString() { return 'amObject'; } },
+    { [Symbol.toPrimitive]: (hint) => 'amObject' },
+  ];
   for (const nonStringValue of nonStringValues) {
     await assert.rejects(
       fileHandle.write(nonStringValue),
diff --git a/test/parallel/test-fs-write-sync-optional-params.js b/test/parallel/test-fs-write-sync-optional-params.js
index 111ce5387b124b..c8659610070819 100644
--- a/test/parallel/test-fs-write-sync-optional-params.js
+++ b/test/parallel/test-fs-write-sync-optional-params.js
@@ -71,6 +71,23 @@ const buffer = Buffer.from('zyx');
       'It must be >= 0 && <= 9007199254740991. Received -1'
   });
 
+  // Test if object is not interpreted as string
+  for (const buffer of [
+    {},
+    new Date(),
+    new String('notPrimitive'),
+    { toString() { return 'amObject'; } },
+    { [Symbol.toPrimitive]: (hint) => 'amObject' },
+  ]) {
+    assert.throws(() => {
+      fs.writeSync(fd, buffer);
+    }, {
+      code: 'ERR_INVALID_ARG_TYPE',
+      name: 'TypeError',
+      message: /^The "buffer" argument must be of type string or an instance of Buffer, TypedArray, or DataView/
+    });
+  }
+
   fs.closeSync(fd);
 
   for (const params of [