diff --git a/core/diyanetdb.py b/core/diyanetdb.py
index e56ad1d..04939ef 100644
--- a/core/diyanetdb.py
+++ b/core/diyanetdb.py
@@ -25,7 +25,7 @@ def get_connection() -> sqlite3.Connection:
             d[col[0]] = row[idx]
         return d
 
-    conn = sqlite3.connect(config.DB_PATH)
+    conn = sqlite3.connect(config.DB_PATH, check_same_thread=False)
     conn.row_factory = dict_factory
     yield conn
     conn.close()
@@ -58,7 +58,7 @@ def save_locations(conn: sqlite3.Connection, locations: List[dict]):
 def find_locations(conn: sqlite3.Connection,
                    *,
                    country: str,
-                   city: str = '') -> List[Location]:
+                   city: str = None) -> List[Location]:
     sql = '''
         SELECT DISTINCT id, country, city, region
         FROM locations