diff --git a/lib/bulk/common.js b/lib/bulk/common.js
index 894d8569c2..fea6c18e34 100644
--- a/lib/bulk/common.js
+++ b/lib/bulk/common.js
@@ -475,7 +475,7 @@ function mergeBatchResults(batch, bulkResult, err, result) {
   if (Array.isArray(result.writeErrors)) {
     for (let i = 0; i < result.writeErrors.length; i++) {
       const writeError = {
-        index: batch.originalIndexes[i],
+        index: batch.originalIndexes[result.writeErrors[i].index],
         code: result.writeErrors[i].code,
         errmsg: result.writeErrors[i].errmsg,
         op: batch.operations[result.writeErrors[i].index]
diff --git a/test/functional/bulk.test.js b/test/functional/bulk.test.js
index 434f48d40b..ff13afa832 100644
--- a/test/functional/bulk.test.js
+++ b/test/functional/bulk.test.js
@@ -1660,4 +1660,41 @@ describe('Bulk', function() {
         );
     });
   });
+
+  it('should preserve order of operation index in unordered bulk operation', function() {
+    const client = this.configuration.newClient();
+    return client.connect().then(() => {
+      this.defer(() => client.close());
+
+      const coll = client.db().collection('bulk_op_ordering_test');
+      function ignoreNsNotFound(err) {
+        if (!err.message.match(/ns not found/)) throw err;
+      }
+
+      return coll
+        .drop()
+        .catch(ignoreNsNotFound)
+        .then(() => {
+          const batch = coll.initializeUnorderedBulkOp();
+          batch.insert({ _id: 1, a: 0 });
+          batch.insert({ _id: 1, a: 0 });
+          batch.insert({ _id: 2, a: 0 });
+          batch.insert({ _id: 2, a: 0 });
+          return batch.execute();
+        })
+        .then(
+          () => {
+            throw new Error('expected a bulk error');
+          },
+          err => {
+            expect(err)
+              .to.have.property('writeErrors')
+              .with.length(2);
+
+            expect(err).to.have.nested.property('writeErrors[0].err.index', 1);
+            expect(err).to.have.nested.property('writeErrors[1].err.index', 3);
+          }
+        );
+    });
+  });
 });