diff --git a/src/transaction_builder.js b/src/transaction_builder.js
index 9e0f54b7d..cf0b9064c 100644
--- a/src/transaction_builder.js
+++ b/src/transaction_builder.js
@@ -487,7 +487,7 @@ export class TransactionBuilder {
       }
 
       let minSeqNum = this.minAccountSequence || '0';
-      minSeqNum = new xdr.SequenceNumber(UnsignedHyper.fromString(minSeqNum));
+      minSeqNum = xdr.SequenceNumber.fromString(minSeqNum);
 
       const minSeqAge = UnsignedHyper.fromString(
         this.minAccountSequenceAge !== null
diff --git a/test/unit/transaction_test.js b/test/unit/transaction_test.js
index e623df684..b1dcbd5eb 100644
--- a/test/unit/transaction_test.js
+++ b/test/unit/transaction_test.js
@@ -738,6 +738,23 @@ describe('Transaction', function() {
       expect(val.toString()).to.equal('5');
     });
 
+    it('minAccountSequence (big number)', function() {
+      let tx = makeBuilder()
+        .setTimeout(5)
+        .setMinAccountSequence('103420918407103888')
+        .build();
+      expect(tx.minAccountSequence).to.eql('103420918407103888');
+
+      const val = tx
+        .toEnvelope()
+        .v1()
+        .tx()
+        .cond()
+        .v2()
+        .minSeqNum();
+      expect(val.toString()).to.equal('103420918407103888');
+    });
+
     it('minAccountSequenceAge', function() {
       let tx = makeBuilder()
         .setTimeout(5)