diff --git a/freqtrade/optimize/__init__.py b/freqtrade/optimize/__init__.py
index 7e44b3bac..967227805 100644
--- a/freqtrade/optimize/__init__.py
+++ b/freqtrade/optimize/__init__.py
@@ -20,6 +20,7 @@ import importlib
 
 logger = logging.getLogger(__name__)
 
+
 def json_load(data):
     """Try to load data with ujson"""
     if _UJSON:
@@ -177,7 +178,7 @@ def load_cached_data_for_updating(filename: str,
     # read the cached file
     if os.path.isfile(filename):
         with open(filename, "rt") as file:
-            data = json.load(file)
+            data = json_load(file)
             # remove the last item, because we are not sure if it is correct
             # it could be fetched when the candle was incompleted
             if data:
@@ -242,4 +243,4 @@ def download_backtesting_testdata(datadir: str,
     logger.debug("New Start: %s", misc.format_ms_time(data[0][0]))
     logger.debug("New End: %s", misc.format_ms_time(data[-1][0]))
 
-    misc.file_dump_json(filename, data)
\ No newline at end of file
+    misc.file_dump_json(filename, data)