diff --git a/freqtrade/freqtradebot.py b/freqtrade/freqtradebot.py
index 7756aa1d7..d0ffddd72 100644
--- a/freqtrade/freqtradebot.py
+++ b/freqtrade/freqtradebot.py
@@ -466,7 +466,7 @@ class FreqtradeBot(LoggingMixin):
             return False
 
     def execute_buy(self, pair: str, stake_amount: float, price: Optional[float] = None,
-                    forcebuy: bool = False, buy_tag: str = '') -> bool:
+                    forcebuy: bool = False, buy_tag: Optional[str] = None) -> bool:
         """
         Executes a limit buy for the given pair
         :param pair: pair for which we want to create a LIMIT_BUY
diff --git a/freqtrade/persistence/models.py b/freqtrade/persistence/models.py
index f42166762..43fbec8c0 100644
--- a/freqtrade/persistence/models.py
+++ b/freqtrade/persistence/models.py
@@ -257,7 +257,7 @@ class LocalTrade():
     sell_reason: str = ''
     sell_order_status: str = ''
     strategy: str = ''
-    buy_tag: str = ''
+    buy_tag: Optional[str] = None
     timeframe: Optional[int] = None
 
     def __init__(self, **kwargs):