diff --git a/progit/model.py b/progit/model.py
index 3192de6..6f80064 100644
--- a/progit/model.py
+++ b/progit/model.py
@@ -188,7 +188,7 @@ class PullRequest(BASE):
         nullable=False)
     start_id = sa.Column(
         sa.String(40),
-        nullable=False)
+        nullable=True)
     stop_id = sa.Column(
         sa.String(40),
         nullable=False)