diff --git a/qtrade/questrade.py b/qtrade/questrade.py
index 5222bad..2a95b96 100644
--- a/qtrade/questrade.py
+++ b/qtrade/questrade.py
@@ -759,4 +759,4 @@ def __del__(self):
 
     @staticmethod
     def _valid_intervals():
-        return set(["OneDay", "OneWeek", "OneMonth", "OneYear"])
+        return set(["FifteenMinutes", "OneDay", "OneWeek", "OneMonth", "OneYear"])