diff --git a/test/parallel/test-os.js b/test/parallel/test-os.js
index b35faeb7cd7bbe..f8e383e497a154 100644
--- a/test/parallel/test-os.js
+++ b/test/parallel/test-os.js
@@ -28,7 +28,7 @@ const { inspect } = require('util');
 
 const is = {
   number: (value, key) => {
-    assert(!isNaN(value), `${key} should not be NaN`);
+    assert(!Number.isNaN(value), `${key} should not be NaN`);
     assert.strictEqual(typeof value, 'number');
   },
   string: (value) => { assert.strictEqual(typeof value, 'string'); },
diff --git a/test/parallel/test-readdouble.js b/test/parallel/test-readdouble.js
index 01ea010609e504..76b259ba498a6d 100644
--- a/test/parallel/test-readdouble.js
+++ b/test/parallel/test-readdouble.js
@@ -72,12 +72,12 @@ function test(clazz) {
   buffer[5] = 0xff;
   buffer[6] = 0x0f;
   buffer[7] = 0x00;
-  assert.ok(isNaN(buffer.readDoubleBE(0)));
+  assert.ok(Number.isNaN(buffer.readDoubleBE(0)));
   assert.strictEqual(2.225073858507201e-308, buffer.readDoubleLE(0));
 
   buffer[6] = 0xef;
   buffer[7] = 0x7f;
-  assert.ok(isNaN(buffer.readDoubleBE(0)));
+  assert.ok(Number.isNaN(buffer.readDoubleBE(0)));
   assert.strictEqual(1.7976931348623157e+308, buffer.readDoubleLE(0));
 
   buffer[0] = 0;
diff --git a/test/parallel/test-writefloat.js b/test/parallel/test-writefloat.js
index c175840f598087..b22b9e8c924899 100644
--- a/test/parallel/test-writefloat.js
+++ b/test/parallel/test-writefloat.js
@@ -127,8 +127,8 @@ function test(clazz) {
   // Darwin ia32 does the other kind of NaN.
   // Compiler bug.  No one really cares.
   assert(0x7F === buffer[7] || 0xFF === buffer[7]);
-  assert.ok(isNaN(buffer.readFloatBE(0)));
-  assert.ok(isNaN(buffer.readFloatLE(4)));
+  assert.ok(Number.isNaN(buffer.readFloatBE(0)));
+  assert.ok(Number.isNaN(buffer.readFloatLE(4)));
 }