diff --git a/freqtrade/data/history/jsondatahandler.py b/freqtrade/data/history/jsondatahandler.py
index 9a02a7769..baa0c10a5 100644
--- a/freqtrade/data/history/jsondatahandler.py
+++ b/freqtrade/data/history/jsondatahandler.py
@@ -37,7 +37,7 @@ class JsonDataHandler(IDataHandler):
         self.create_dir_if_needed(filename)
         _data = data.copy()
         # Convert date to int
-        _data['date'] = _data['date'].view(np.int64) // 1000 // 1000
+        _data['date'] = _data['date'].astype(np.int64) // 1000 // 1000
 
         # Reset index, select only appropriate columns and save as json
         _data.reset_index(drop=True).loc[:, self._columns].to_json(
diff --git a/freqtrade/rpc/rpc.py b/freqtrade/rpc/rpc.py
index 2317ee1a9..6e8447d29 100644
--- a/freqtrade/rpc/rpc.py
+++ b/freqtrade/rpc/rpc.py
@@ -1155,7 +1155,7 @@ class RPC:
         }
         if has_content:
 
-            dataframe.loc[:, '__date_ts'] = dataframe.loc[:, 'date'].view(int64) // 1000 // 1000
+            dataframe.loc[:, '__date_ts'] = dataframe.loc[:, 'date'].astype(int64) // 1000 // 1000
             # Move signal close to separate column when signal for easy plotting
             for sig_type in signals.keys():
                 if sig_type in dataframe.columns:
diff --git a/tests/conftest.py b/tests/conftest.py
index 9c81c050d..a322bfd77 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -177,7 +177,7 @@ def generate_test_data(timeframe: str, size: int, start: str = '2020-07-05'):
 def generate_test_data_raw(timeframe: str, size: int, start: str = '2020-07-05'):
     """ Generates data in the ohlcv format used by ccxt """
     df = generate_test_data(timeframe, size, start)
-    df['date'] = df.loc[:, 'date'].view(np.int64) // 1000 // 1000
+    df['date'] = df.loc[:, 'date'].astype(np.int64) // 1000 // 1000
     return list(list(x) for x in zip(*(df[x].values.tolist() for x in df.columns)))