diff --git a/lib/crypto/bn.js b/lib/crypto/bn.js
index a1d381c..20b53f8 100644
--- a/lib/crypto/bn.js
+++ b/lib/crypto/bn.js
@@ -21,9 +21,9 @@ BN.fromNumber = function(n) {
   return new BN(n);
 };
 
-BN.fromString = function(str) {
+BN.fromString = function(str, base) {
   $.checkArgument(_.isString(str));
-  return new BN(str);
+  return new BN(str, base);
 };
 
 BN.fromBuffer = function(buf, opts) {
diff --git a/test/crypto/bn.js b/test/crypto/bn.js
index a57260d..085b40c 100644
--- a/test/crypto/bn.js
+++ b/test/crypto/bn.js
@@ -79,6 +79,10 @@ describe('BN', function() {
     it('should make BN from a string', function() {
       BN.fromString('5').toString().should.equal('5');
     });
+    it('should work with hex string', function() {
+      BN.fromString('7fffff0000000000000000000000000000000000000000000000000000000000', 16)
+      .toString(16).should.equal('7fffff0000000000000000000000000000000000000000000000000000000000');
+    });
   });
 
   describe('#toString', function() {