diff --git a/lib/hdprivatekey.js b/lib/hdprivatekey.js
index 230dc03..989a723 100644
--- a/lib/hdprivatekey.js
+++ b/lib/hdprivatekey.js
@@ -4,6 +4,7 @@
 var assert = require('assert');
 var buffer = require('buffer');
 var _ = require('lodash');
+var $ = require('./util/preconditions');
 
 var BN = require('./crypto/bn');
 var Base58 = require('./encoding/base58');
@@ -277,7 +278,18 @@ HDPrivateKey._validateNetwork = function(data, networkArg) {
   return null;
 };
 
-HDPrivateKey.fromJSON = HDPrivateKey.fromObject = HDPrivateKey.fromString = function(arg) {
+HDPrivateKey.fromJSON = function(arg) {
+  $.checkArgument(JSUtil.isValidJSON(arg), 'No valid JSON string was provided');
+  return new HDPrivateKey(arg);
+};
+
+HDPrivateKey.fromString = function(arg) {
+  $.checkArgument(_.isString(arg), 'No valid string was provided');
+  return new HDPrivateKey(arg);
+};
+
+HDPrivateKey.fromObject = function(arg) {
+  $.checkArgument(_.isObject(arg), 'No valid argument was provided');
   return new HDPrivateKey(arg);
 };
 
diff --git a/lib/util/js.js b/lib/util/js.js
index 9366510..be6f366 100644
--- a/lib/util/js.js
+++ b/lib/util/js.js
@@ -29,6 +29,9 @@ module.exports = {
    */
   isValidJSON: function isValidJSON(arg) {
     var parsed;
+    if (!_.isString(arg)) {
+      return false;
+    }
     try {
       parsed = JSON.parse(arg);
     } catch (e) {
diff --git a/test/hdprivatekey.js b/test/hdprivatekey.js
index 665eb37..3c47898 100644
--- a/test/hdprivatekey.js
+++ b/test/hdprivatekey.js
@@ -78,14 +78,39 @@ describe('HDPrivate key interface', function() {
     ));
   });
 
-  describe('should error with a nonsensical argument', function() {
-    it('like a number', function() {
+  describe('instantiation', function() {
+    it('invalid argument: can not instantiate from a number', function() {
       expectFailBuilding(1, hdErrors.UnrecognizedArgument);
     });
-  });
-
-  it('allows no-new calling', function() {
-    HDPrivateKey(xprivkey).toString().should.equal(xprivkey);
+    it('allows no-new calling', function() {
+      HDPrivateKey(xprivkey).toString().should.equal(xprivkey);
+    });
+    var expectStaticMethodFail = function(staticMethod, argument, message) {
+      expect(HDPrivateKey[staticMethod].bind(null, argument)).to.throw(message);
+    };
+    it('fromJSON checks that a valid JSON is provided', function() {
+      var errorMessage = 'No valid JSON string was provided';
+      var method = 'fromJSON';
+      expectStaticMethodFail(method, undefined, errorMessage); 
+      expectStaticMethodFail(method, null, errorMessage); 
+      expectStaticMethodFail(method, 'invalid JSON', errorMessage); 
+      expectStaticMethodFail(method, '{\'singlequotes\': true}', errorMessage); 
+      expectStaticMethodFail(method, {}, errorMessage); 
+    });
+    it('fromString checks that a string is provided', function() {
+      var errorMessage = 'No valid string was provided';
+      var method = 'fromString';
+      expectStaticMethodFail(method, undefined, errorMessage); 
+      expectStaticMethodFail(method, null, errorMessage); 
+      expectStaticMethodFail(method, {}, errorMessage); 
+    });
+    it('fromObject checks that an object is provided', function() {
+      var errorMessage = 'No valid argument was provided';
+      var method = 'fromObject';
+      expectStaticMethodFail(method, undefined, errorMessage); 
+      expectStaticMethodFail(method, null, errorMessage); 
+      expectStaticMethodFail(method, '', errorMessage); 
+    });
   });
 
   it('inspect() displays correctly', function() {