diff --git a/corrlib/integrity.py b/corrlib/integrity.py
index 8a414bf..d865944 100644
--- a/corrlib/integrity.py
+++ b/corrlib/integrity.py
@@ -5,7 +5,7 @@ import pandas as pd
 import sqlite3
 
 
-def has_valid_times(result: pd.DataFrame) -> bool:
+def has_valid_times(result: pd.Series) -> bool:
     # we expect created_at <= updated_at <= now
     created_at = dt.datetime.fromisoformat(result['created_at'])
     updated_at = dt.datetime.fromisoformat(result['updated_at'])
@@ -34,7 +34,7 @@ def check_db_integrity(path: Path) -> None:
     conn = sqlite3.connect(db)
     results = pd.read_sql(search_expr, conn)
 
-    for result in results:
+    for _, result in results.iterrows():
         if not has_valid_times(result):
             raise ValueError(f"Result with id {result[id]} has wrong time signatures.")