diff --git a/stdimage/validators.py b/stdimage/validators.py
index f0abd7d..b609c55 100644
--- a/stdimage/validators.py
+++ b/stdimage/validators.py
@@ -28,8 +28,9 @@ def __call__(self, value):
     def clean(value):
         value.seek(0)
         stream = BytesIO(value.read())
-        img = Image.open(stream)
-        return img.size
+        size = Image.open(stream).size
+        value.seek(0)
+        return size
 
 
 class MaxSizeValidator(BaseSizeValidator):
diff --git a/tests/test_models.py b/tests/test_models.py
index 021c912..f681e7a 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -227,15 +227,17 @@ def test_render_variations_overwrite(self, db, image_upload_file):
 
 class TestValidators(TestStdImage):
     def test_max_size_validator(self, admin_client):
-        admin_client.post('/admin/tests/maxsizemodel/add/', {
+        response = admin_client.post('/admin/tests/maxsizemodel/add/', {
             'image': self.fixtures['600x400.jpg'],
         })
+        assert 'too large' in response.context['adminform'].form.errors['image'][0]
         assert not os.path.exists(os.path.join(IMG_DIR, '800x600.jpg'))
 
     def test_min_size_validator(self, admin_client):
-        admin_client.post('/admin/tests/minsizemodel/add/', {
+        response = admin_client.post('/admin/tests/minsizemodel/add/', {
             'image': self.fixtures['100.gif'],
         })
+        assert 'too small' in response.context['adminform'].form.errors['image'][0]
         assert not os.path.exists(os.path.join(IMG_DIR, '100.gif'))