diff --git a/freqtrade/optimize/hyperopt.py b/freqtrade/optimize/hyperopt.py
index d28373c2f..11a1a36f2 100644
--- a/freqtrade/optimize/hyperopt.py
+++ b/freqtrade/optimize/hyperopt.py
@@ -271,7 +271,7 @@ class Hyperopt:
             self.backtesting.strategy.trailing_only_offset_is_reached = \
                 d['trailing_only_offset_is_reached']
 
-        processed = load(self.data_pickle_file, mmap_mode='r+')
+        processed = load(self.data_pickle_file, mmap_mode='r')
 
         bt_results = self.backtesting.backtest(
             processed=processed,