diff --git a/test/parallel/test-buffer-readint.js b/test/parallel/test-buffer-readint.js
index d417f88b82fe73..971dd3bb959444 100644
--- a/test/parallel/test-buffer-readint.js
+++ b/test/parallel/test-buffer-readint.js
@@ -160,7 +160,7 @@ const assert = require('assert');
   });
 
   // Test 1 to 6 bytes.
-  for (let i = 1; i < 6; i++) {
+  for (let i = 1; i <= 6; i++) {
     ['readIntBE', 'readIntLE'].forEach((fn) => {
       ['', '0', null, {}, [], () => {}, true, false, undefined].forEach((o) => {
         assert.throws(
diff --git a/test/parallel/test-buffer-readuint.js b/test/parallel/test-buffer-readuint.js
index d2c07e4de87f89..de683f09503eff 100644
--- a/test/parallel/test-buffer-readuint.js
+++ b/test/parallel/test-buffer-readuint.js
@@ -128,7 +128,7 @@ const assert = require('assert');
   });
 
   // Test 1 to 6 bytes.
-  for (let i = 1; i < 6; i++) {
+  for (let i = 1; i <= 6; i++) {
     ['readUIntBE', 'readUIntLE'].forEach((fn) => {
       ['', '0', null, {}, [], () => {}, true, false, undefined].forEach((o) => {
         assert.throws(
diff --git a/test/parallel/test-buffer-writeint.js b/test/parallel/test-buffer-writeint.js
index fb91aa11b6f995..0e5b4960ab234d 100644
--- a/test/parallel/test-buffer-writeint.js
+++ b/test/parallel/test-buffer-writeint.js
@@ -162,6 +162,21 @@ const errorOutOfBounds = common.expectsError({
   });
 }
 
+// Test 48 bit
+{
+  const value = 0x1234567890ab;
+  const buffer = Buffer.allocUnsafe(6);
+  buffer.writeIntBE(value, 0, 6);
+  assert.ok(buffer.equals(new Uint8Array([
+    0x12, 0x34, 0x56, 0x78, 0x90, 0xab
+  ])));
+
+  buffer.writeIntLE(value, 0, 6);
+  assert.ok(buffer.equals(new Uint8Array([
+    0xab, 0x90, 0x78, 0x56, 0x34, 0x12
+  ])));
+}
+
 // Test Int
 {
   const data = Buffer.alloc(8);
diff --git a/test/parallel/test-buffer-writeuint.js b/test/parallel/test-buffer-writeuint.js
index 8fe7783e71be04..999440114c74f4 100644
--- a/test/parallel/test-buffer-writeuint.js
+++ b/test/parallel/test-buffer-writeuint.js
@@ -110,6 +110,17 @@ const assert = require('assert');
   assert.ok(data.equals(new Uint8Array([0x6d, 0x6d, 0x6d, 0x0a, 0xf9, 0xe7])));
 }
 
+// Test 48 bit
+{
+  const value = 0x1234567890ab;
+  const data = Buffer.allocUnsafe(6);
+  data.writeUIntBE(value, 0, 6);
+  assert.ok(data.equals(new Uint8Array([0x12, 0x34, 0x56, 0x78, 0x90, 0xab])));
+
+  data.writeUIntLE(value, 0, 6);
+  assert.ok(data.equals(new Uint8Array([0xab, 0x90, 0x78, 0x56, 0x34, 0x12])));
+}
+
 // Test UInt
 {
   const data = Buffer.alloc(8);