diff --git a/influxdb/_dataframe_client.py b/influxdb/_dataframe_client.py
index d16e29ca..277129ce 100644
--- a/influxdb/_dataframe_client.py
+++ b/influxdb/_dataframe_client.py
@@ -371,7 +371,8 @@ def _convert_dataframe_to_lines(self,
             del tag_df
         elif global_tags:
             tag_string = ''.join(
-                [",{}={}".format(k, _escape_tag(v)) if v else ''
+                [",{}={}".format(k, _escape_tag(v)) 
+                 if v not in [None, ''] else ""
                  for k, v in sorted(global_tags.items())]
             )
             tags = pd.Series(tag_string, index=dataframe.index)