diff --git a/flaschengeist/models/user.py b/flaschengeist/models/user.py
index d2eea8f..2ce1716 100644
--- a/flaschengeist/models/user.py
+++ b/flaschengeist/models/user.py
@@ -53,7 +53,7 @@ class User(db.Model, ModelSerializeMixin):
     """
 
     __tablename__ = "user"
-    userid: str = db.Column(db.String(30), nullable=False)
+    userid: str = db.Column(db.String(30), unique=True, nullable=False)
     display_name: str = db.Column(db.String(30))
     firstname: str = db.Column(db.String(50), nullable=False)
     lastname: str = db.Column(db.String(50), nullable=False)