diff --git a/aurora/models.py b/aurora/models.py
index dad4028..52cf3b7 100644
--- a/aurora/models.py
+++ b/aurora/models.py
@@ -131,7 +131,7 @@ class Change(AuroraBaseModel):
         if "duration" in data and data["duration"] and not isinstance(data["duration"], timedelta):
             hours, minutes, seconds = map(int, data["duration"].split(':'))
             duration = timedelta(hours=hours, minutes=minutes, seconds=seconds)
-        elif duration in data and isinstance(data["duration"], timedelta):
+        elif "duration" in data and isinstance(data["duration"], timedelta):
             duration = data["duration"]
         else:
             duration = None