diff --git a/lib/util.js b/lib/util.js
index f84f528ce3..86f585f952 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -566,11 +566,7 @@ exports.isFunction = isFunction;
 
 function isPrimitive(arg) {
   return arg === null ||
-         typeof arg === 'boolean' ||
-         typeof arg === 'number' ||
-         typeof arg === 'string' ||
-         typeof arg === 'symbol' ||  // ES6 symbol
-         typeof arg === 'undefined';
+         typeof arg !== 'object' && typeof arg !== 'function';
 }
 exports.isPrimitive = isPrimitive;
 
diff --git a/test/parallel/test-util.js b/test/parallel/test-util.js
index d8966ce669..2fb4bc5609 100644
--- a/test/parallel/test-util.js
+++ b/test/parallel/test-util.js
@@ -51,6 +51,25 @@ assert.equal(true, util.isError(Object.create(Error.prototype)));
 // isObject
 assert.ok(util.isObject({}) === true);
 
+// isPrimitive
+assert.equal(false, util.isPrimitive({}));
+assert.equal(false, util.isPrimitive(new Error));
+assert.equal(false, util.isPrimitive(new Date()));
+assert.equal(false, util.isPrimitive([]));
+assert.equal(false, util.isPrimitive(/regexp/));
+assert.equal(false, util.isPrimitive(function(){}));
+assert.equal(false, util.isPrimitive(new Number(1)));
+assert.equal(false, util.isPrimitive(new String('bla')));
+assert.equal(false, util.isPrimitive(new Boolean(true)));
+assert.equal(true, util.isPrimitive(1));
+assert.equal(true, util.isPrimitive('bla'));
+assert.equal(true, util.isPrimitive(true));
+assert.equal(true, util.isPrimitive(undefined));
+assert.equal(true, util.isPrimitive(null));
+assert.equal(true, util.isPrimitive(Infinity));
+assert.equal(true, util.isPrimitive(NaN));
+assert.equal(true, util.isPrimitive(Symbol('symbol')));
+
 // _extend
 assert.deepEqual(util._extend({a:1}),             {a:1});
 assert.deepEqual(util._extend({a:1}, []),         {a:1});