diff --git a/freqtrade/data/entryexitanalysis.py b/freqtrade/data/entryexitanalysis.py
index c72def0ac..fff051f1c 100644
--- a/freqtrade/data/entryexitanalysis.py
+++ b/freqtrade/data/entryexitanalysis.py
@@ -211,7 +211,7 @@ def prepare_results(analysed_trades, stratname,
                     timerange=None):
     res_df = pd.DataFrame()
     for pair, trades in analysed_trades[stratname].items():
-        trades.dropna(subset['close_date'], inplace=True)
+        trades.dropna(subset=['close_date'], inplace=True)
         res_df = pd.concat([res_df, trades], ignore_index=True)
 
     res_df = _select_rows_within_dates(res_df, timerange)