diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 82a4c5e..e5c5bd8 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -12,14 +12,18 @@ Change Log
 .. There should always be an "Unreleased" section for changes pending release.
 
 Unreleased
-[0.8.14] - 2021-07-12
-* Update csv import error message
+[0.9.1] - 2021-08-02
+* Feat repeat user error should also show the first occurence
 ~~~~~~~~~~
 
 [0.9.0] - 2021-07-20
 ~~~~~~~~~~~~~~~~~~~~
 * Added support for django 3.2
 
+[0.8.14] - 2021-07-12
+* Update csv import error message
+=======
+
 [0.8.13] - 2021-07-12
 ~~~~~~~~~~~~~~~~~~~~~
 * Fix bug where we ignore repeat user in the csv import
diff --git a/bulk_grades/__init__.py b/bulk_grades/__init__.py
index 88f161a..f8e88d4 100644
--- a/bulk_grades/__init__.py
+++ b/bulk_grades/__init__.py
@@ -2,6 +2,6 @@
 Support for bulk scoring and grading.
 """
 
-__version__ = '0.9.0'
+__version__ = '0.9.1'
 
 default_app_config = 'bulk_grades.apps.BulkGradesConfig'  # pylint: disable=invalid-name
diff --git a/bulk_grades/api.py b/bulk_grades/api.py
index e0f04ee..7be51f4 100644
--- a/bulk_grades/api.py
+++ b/bulk_grades/api.py
@@ -4,7 +4,7 @@
 
 
 import logging
-from collections import OrderedDict
+from collections import OrderedDict, defaultdict
 from itertools import product
 
 from django.apps import apps
@@ -316,7 +316,8 @@ def __init__(self, **kwargs):
                 self.subsection_prefixes
             )
         )
-        self._users_seen = set()
+        self._users_seen = defaultdict(list)
+        self._row_num = 0
 
     # pylint: disable=inconsistent-return-statements
     @cached_property
@@ -349,6 +350,7 @@ def preprocess_file(self, reader):
         """
         Preprocess the file, saving original data no matter whether there are errors.
         """
+        self._row_num = 0   # reset private row number count
         super().preprocess_file(reader)
         self.save()
 
@@ -356,10 +358,15 @@ def preprocess_row(self, row):
         """
         Preprocess the CSV row.
         """
+        self._row_num += 1
         operation = {}
         user_id = row['user_id']
         if user_id in self._users_seen:
+            if len(self._users_seen[user_id]) == 1:
+                self.add_error(_('Repeated user_id: ') + str(user_id), self._users_seen[user_id][0])
+            self._users_seen[user_id].append(self._row_num)
             raise ValidationError(_('Repeated user_id: ') + str(user_id))
+        self._users_seen[user_id].append(self._row_num)
 
         operation['new_override_grades'] = []
         operation['course_id'] = self.course_id
@@ -381,7 +388,6 @@ def preprocess_row(self, row):
                             raise ValidationError(_('Grade must not be negative'))
                         operation['new_override_grades'].append((block_id, new_grade))
 
-        self._users_seen.add(user_id)
         return operation
 
     def process_row(self, row):
diff --git a/tests/test_api.py b/tests/test_api.py
index ea25537..cd848bf 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -442,7 +442,7 @@ def test_course_grade_filters(self, course_grade_factory_mock):
         rows = list(processor.get_iterator())
         self.assertEqual(len(rows), (self.NUM_USERS - 2)+1)
 
-    def test_preprocess_error(self):
+    def test_preprocess_negative_number_error(self):
         processor = api.GradeCSVProcessor(course_id=self.course_id)
         row = {
             'block_id': self.usage_key,
@@ -454,7 +454,17 @@ def test_preprocess_error(self):
         }
         with self.assertRaisesMessage(ValidationError, 'Grade must not be negative'):
             processor.preprocess_row(row)
-        row['new_override-85bb02db'] = 'not a number'
+
+    def test_preprocess_nan_error(self):
+        processor = api.GradeCSVProcessor(course_id=self.course_id)
+        row = {
+            'block_id': self.usage_key,
+            'new_override-123402db': '1',
+            'new_override-85bb02db': 'not a number',
+            'user_id': self.learner.id,
+            'csum': '07ec',
+            'Previous Points': '',
+        }
         with self.assertRaisesMessage(ValueError, 'Grade must be a number'):
             processor.preprocess_row(row)
 
@@ -497,6 +507,13 @@ def test_repeat_user(self):
         # different row with the same user id throw error
         with self.assertRaisesMessage(ValidationError, 'Repeated user'):
             processor.preprocess_row(row2)
+            # there should be 2 errors for the first repeat user error
+            self.assertCountEqual(len(processor.error_messages), 2)
+        
+        with self.assertRaisesMessage(ValidationError, 'Repeated user'):
+            processor.preprocess_row(row2)
+            # there should be 3 errors for the second repeat user error
+            self.assertCountEqual(len(processor.error_messages), 3)
 
     def test_empty_grade(self):
         processor = api.GradeCSVProcessor(course_id=self.course_id)