diff --git a/test/parallel/test-buffer-bytelength.js b/test/parallel/test-buffer-bytelength.js
index b14047893370f2..09e59743e40208 100644
--- a/test/parallel/test-buffer-bytelength.js
+++ b/test/parallel/test-buffer-bytelength.js
@@ -106,3 +106,12 @@ assert.strictEqual(Buffer.byteLength('Il était tué', 'utf8'), 14);
 // Test that ArrayBuffer from a different context is detected correctly
 const arrayBuf = vm.runInNewContext('new ArrayBuffer()');
 assert.strictEqual(Buffer.byteLength(arrayBuf), 0);
+
+// Verify that invalid encodings are treated as utf8
+for (let i = 1; i < 10; i++) {
+  const encoding = String(i).repeat(i);
+
+  assert.ok(!Buffer.isEncoding(encoding));
+  assert.strictEqual(Buffer.byteLength('foo', encoding),
+                     Buffer.byteLength('foo', 'utf8'));
+}
diff --git a/test/parallel/test-buffer-tostring.js b/test/parallel/test-buffer-tostring.js
index 776b7c089224ed..214d1013e9896c 100644
--- a/test/parallel/test-buffer-tostring.js
+++ b/test/parallel/test-buffer-tostring.js
@@ -4,8 +4,8 @@ require('../common');
 const assert = require('assert');
 
 // utf8, ucs2, ascii, latin1, utf16le
-const encodings = ['utf8', 'ucs2', 'ucs-2', 'ascii', 'latin1', 'binary',
-                   'utf16le', 'utf-16le'];
+const encodings = ['utf8', 'utf-8', 'ucs2', 'ucs-2', 'ascii', 'latin1',
+                   'binary', 'utf16le', 'utf-16le'];
 
 encodings
   .reduce((es, e) => es.concat(e, e.toUpperCase()), [])
@@ -23,3 +23,12 @@ encodings
   assert.strictEqual(Buffer.from('666f6f', encoding).toString(encoding),
                      '666f6f');
 });
+
+// Invalid encodings
+for (let i = 1; i < 10; i++) {
+  const encoding = String(i).repeat(i);
+  const error = new RegExp(`^TypeError: Unknown encoding: ${encoding}$`);
+
+  assert.ok(!Buffer.isEncoding(encoding));
+  assert.throws(() => Buffer.from('foo').toString(encoding), error);
+}
diff --git a/test/parallel/test-buffer-write.js b/test/parallel/test-buffer-write.js
index 80c95dda4471e7..f278b92cce957c 100644
--- a/test/parallel/test-buffer-write.js
+++ b/test/parallel/test-buffer-write.js
@@ -53,3 +53,12 @@ encodings
   assert.strictEqual(buf.write('666f6f', 0, len, encoding), len);
   assert.deepStrictEqual(buf, resultMap.get(encoding.toLowerCase()));
 });
+
+// Invalid encodings
+for (let i = 1; i < 10; i++) {
+  const encoding = String(i).repeat(i);
+  const error = new RegExp(`^TypeError: Unknown encoding: ${encoding}$`);
+
+  assert.ok(!Buffer.isEncoding(encoding));
+  assert.throws(() => Buffer.alloc(9).write('foo', encoding), error);
+}