diff --git a/SAS/TriggerEmailService/Server/lib/TriggerEmailService.py b/SAS/TriggerEmailService/Server/lib/TriggerEmailService.py
index 1598508818c64bc485f89945e3730cfd165cae56..418f1345535606cb6abc61e664193d3fc216f7b7 100644
--- a/SAS/TriggerEmailService/Server/lib/TriggerEmailService.py
+++ b/SAS/TriggerEmailService/Server/lib/TriggerEmailService.py
@@ -41,7 +41,7 @@ from lofar.sas.TriggerEmailService.common.config import DEFAULT_TRIGGER_NOTIFICA
 from lofar.sas.TriggerEmailService.common.config import DEFAULT_TRIGGER_NOTIFICATION_SUBJECT
 from lofar.mom.momqueryservice.momqueryrpc import MoMQueryRPC
 from lxml import etree
-from io import StringIO
+from io import BytesIO
 from re import findall
 import socket
 
@@ -235,7 +235,7 @@ class TriggerNotificationListener(AbstractBusListener):
 
     def _get_observation_start_stop_times(self, trigger_xml):
         # for now we work with duration to get stop time
-        doc = etree.parse(StringIO(trigger_xml.encode('UTF-8')))
+        doc = etree.parse(BytesIO(trigger_xml.encode('UTF-8')))
 
         start_times = doc.getroot().findall('specification/activity/observation/timeWindowSpecification/startTime')