diff --git a/tableauserverclient/models/interval_item.py b/tableauserverclient/models/interval_item.py
index 14cec187..52fd658c 100644
--- a/tableauserverclient/models/interval_item.py
+++ b/tableauserverclient/models/interval_item.py
@@ -318,4 +318,4 @@ def interval(self, interval_values):
         self._interval = interval_values
 
     def _interval_type_pairs(self):
-        return [(IntervalItem.Occurrence.MonthDay, self.interval)]
+        return [(IntervalItem.Occurrence.MonthDay, str(day)) for day in self.interval]