diff --git a/bingads/v13/bulk/entities/ad_extensions/bulk_filterlink_ad_extensions.py b/bingads/v13/bulk/entities/ad_extensions/bulk_filterlink_ad_extensions.py
index 79444539..88fbbef6 100644
--- a/bingads/v13/bulk/entities/ad_extensions/bulk_filterlink_ad_extensions.py
+++ b/bingads/v13/bulk/entities/ad_extensions/bulk_filterlink_ad_extensions.py
@@ -69,7 +69,7 @@ def filter_link_ad_extension(self, value):
         ),
         _SimpleBulkMapping(
             header=_StringTable.TrackingTemplate,
-            field_to_csv=lambda c: bulk_str(c.filter_link_ad_extension.TrackingUrlTemplate),
+            field_to_csv=lambda c: bulk_optional_str(c.filter_link_ad_extension.TrackingUrlTemplate),
             csv_to_field=lambda c, v: setattr(c.filter_link_ad_extension, 'TrackingUrlTemplate', v if v else None)
         ),
         _SimpleBulkMapping(
diff --git a/bingads/v13/bulk/entities/ad_extensions/bulk_flyer_ad_extensions.py b/bingads/v13/bulk/entities/ad_extensions/bulk_flyer_ad_extensions.py
index 28a95189..c2e49deb 100644
--- a/bingads/v13/bulk/entities/ad_extensions/bulk_flyer_ad_extensions.py
+++ b/bingads/v13/bulk/entities/ad_extensions/bulk_flyer_ad_extensions.py
@@ -79,7 +79,7 @@ def flyer_ad_extension(self, value):
         ),
         _SimpleBulkMapping(
             header=_StringTable.TrackingTemplate,
-            field_to_csv=lambda c: bulk_str(c.flyer_ad_extension.TrackingUrlTemplate),
+            field_to_csv=lambda c: bulk_optional_str(c.flyer_ad_extension.TrackingUrlTemplate),
             csv_to_field=lambda c, v: setattr(c.flyer_ad_extension, 'TrackingUrlTemplate', v if v else None)
         ),
         _SimpleBulkMapping(
diff --git a/bingads/v13/bulk/entities/ad_extensions/bulk_price_ad_extensions.py b/bingads/v13/bulk/entities/ad_extensions/bulk_price_ad_extensions.py
index 3b2cbaa8..7c107918 100644
--- a/bingads/v13/bulk/entities/ad_extensions/bulk_price_ad_extensions.py
+++ b/bingads/v13/bulk/entities/ad_extensions/bulk_price_ad_extensions.py
@@ -66,7 +66,7 @@ def price_ad_extension(self, value):
         ),
         _SimpleBulkMapping(
             header=_StringTable.TrackingTemplate,
-            field_to_csv=lambda c: bulk_str(c.price_ad_extension.TrackingUrlTemplate),
+            field_to_csv=lambda c: bulk_optional_str(c.price_ad_extension.TrackingUrlTemplate),
             csv_to_field=lambda c, v: setattr(c.price_ad_extension, 'TrackingUrlTemplate', v if v else None)
         ),
         _SimpleBulkMapping(
diff --git a/bingads/v13/bulk/entities/ad_extensions/bulk_sitelink_ad_extensions.py b/bingads/v13/bulk/entities/ad_extensions/bulk_sitelink_ad_extensions.py
index c91838b2..65ef9e3b 100644
--- a/bingads/v13/bulk/entities/ad_extensions/bulk_sitelink_ad_extensions.py
+++ b/bingads/v13/bulk/entities/ad_extensions/bulk_sitelink_ad_extensions.py
@@ -85,7 +85,7 @@ def sitelink_ad_extension(self, value):
         ),
         _SimpleBulkMapping(
             header=_StringTable.TrackingTemplate,
-            field_to_csv=lambda c: bulk_str(c.sitelink_ad_extension.TrackingUrlTemplate),
+            field_to_csv=lambda c: bulk_optional_str(c.sitelink_ad_extension.TrackingUrlTemplate),
             csv_to_field=lambda c, v: setattr(c.sitelink_ad_extension, 'TrackingUrlTemplate', v if v else None)
         ),
         _SimpleBulkMapping(
diff --git a/bingads/v13/bulk/entities/ad_extensions/bulk_video_ad_extensions.py b/bingads/v13/bulk/entities/ad_extensions/bulk_video_ad_extensions.py
index a0dfa3e9..31db1375 100644
--- a/bingads/v13/bulk/entities/ad_extensions/bulk_video_ad_extensions.py
+++ b/bingads/v13/bulk/entities/ad_extensions/bulk_video_ad_extensions.py
@@ -94,7 +94,7 @@ def video_ad_extension(self, value):
         ),
         _SimpleBulkMapping(
             header=_StringTable.TrackingTemplate,
-            field_to_csv=lambda c: bulk_str(c.video_ad_extension.TrackingUrlTemplate),
+            field_to_csv=lambda c: bulk_optional_str(c.video_ad_extension.TrackingUrlTemplate),
             csv_to_field=lambda c, v: setattr(c.video_ad_extension, 'TrackingUrlTemplate', v if v else None)
         ),
         _SimpleBulkMapping(
diff --git a/bingads/v13/bulk/entities/audiences/bulk_product_audience.py b/bingads/v13/bulk/entities/audiences/bulk_product_audience.py
index 45bd2bbd..8b07b06c 100644
--- a/bingads/v13/bulk/entities/audiences/bulk_product_audience.py
+++ b/bingads/v13/bulk/entities/audiences/bulk_product_audience.py
@@ -34,7 +34,7 @@ def __init__(self,
             csv_to_field=lambda c, v: setattr(c.product_audience, 'TagId', int(v) if v else None)
         ),
         _SimpleBulkMapping(
-            _StringTable.Audience,
+            _StringTable.ProductAudienceType,
             field_to_csv=lambda c: bulk_str(c.product_audience.ProductAudienceType),
             csv_to_field=lambda c, v: setattr(c.product_audience, 'ProductAudienceType', v)
         ),
diff --git a/bingads/v13/bulk/entities/bulk_ads.py b/bingads/v13/bulk/entities/bulk_ads.py
index bb222667..b6b7ab32 100644
--- a/bingads/v13/bulk/entities/bulk_ads.py
+++ b/bingads/v13/bulk/entities/bulk_ads.py
@@ -165,7 +165,7 @@ def ad(self, ad):
         ),
         _SimpleBulkMapping(
             header=_StringTable.TrackingTemplate,
-            field_to_csv=lambda c: bulk_str(c.ad.TrackingUrlTemplate),
+            field_to_csv=lambda c: bulk_optional_str(c.ad.TrackingUrlTemplate),
             csv_to_field=lambda c, v: setattr(c.ad, 'TrackingUrlTemplate', v if v else None)
         ),
         _SimpleBulkMapping(
@@ -807,4 +807,4 @@ def process_mappings_from_row_values(self, row_values):
     def process_mappings_to_row_values(self, row_values, exclude_readonly_data):
         self._validate_property_not_null(self.responsive_search_ad, 'responsive_search_ad')
         super(BulkResponsiveSearchAd, self).process_mappings_to_row_values(row_values, exclude_readonly_data)
-        self.convert_to_values(row_values, BulkResponsiveSearchAd._MAPPINGS)
\ No newline at end of file
+        self.convert_to_values(row_values, BulkResponsiveSearchAd._MAPPINGS)