diff --git a/backend/app/auth.py b/backend/app/auth.py
index b250747..09d0770 100644
--- a/backend/app/auth.py
+++ b/backend/app/auth.py
@@ -90,11 +90,19 @@ def get_user_from_token(token: str) -> Optional[dict]:
 
 
 def ensure_admin_exists():
-    """Called on startup — creates the admin user if no users exist."""
+    """Called on startup — creates the admin user if no users exist,
+    and ensures the 'default' campaign is owned by the admin."""
     conn = db.get_conn()
     row = conn.execute("SELECT COUNT(*) as cnt FROM users").fetchone()
-    if row["cnt"] > 0:
-        return
-    pw = ADMIN_PASSWORD or os.urandom(8).hex()
-    db.create_user(ADMIN_USERNAME, hash_password(pw), is_admin=True)
-    print(f"[auth] Created admin user '{ADMIN_USERNAME}' (password: {pw})")
+    if row["cnt"] == 0:
+        pw = ADMIN_PASSWORD or os.urandom(8).hex()
+        db.create_user(ADMIN_USERNAME, hash_password(pw), is_admin=True)
+        print(f"[auth] Created admin user '{ADMIN_USERNAME}' (password: {pw})")
+
+    # Claim the "default" campaign for the admin so setup wizard works
+    admin = db.get_user_by_username(ADMIN_USERNAME)
+    if admin:
+        conn.execute(
+            "UPDATE campaigns SET created_by = ? WHERE id = 'default' AND created_by IS NULL",
+            (admin["id"],),
+        )