diff --git a/freqtrade/main.py b/freqtrade/main.py
index 7a71ca414..60f561c7a 100755
--- a/freqtrade/main.py
+++ b/freqtrade/main.py
@@ -36,7 +36,7 @@ def refresh_whitelist(whitelist: List[str]) -> List[str]:
     health = exchange.get_wallet_health()
     for status in health:
         pair = '{}_{}'.format(_CONF['stake_currency'], status['Currency'])
-        if pair not in whitelist or pair in _CONF['exchange'].get('pair_blacklist',[]):
+        if pair not in whitelist or pair in _CONF['exchange'].get('pair_blacklist', []):
             continue
         if status['IsActive']:
             sanitized_whitelist.append(pair)
@@ -47,6 +47,7 @@ def refresh_whitelist(whitelist: List[str]) -> List[str]:
             )
     return sanitized_whitelist
 
+
 def _process(nb_assets: Optional[int] = 0) -> bool:
     """
     Queries the persistence layer for open trades and handles them,
@@ -64,7 +65,8 @@ def _process(nb_assets: Optional[int] = 0) -> bool:
         )
 
         # Keep only the subsets of pairs wanted (up to nb_assets)
-        _CONF['exchange']['pair_whitelist'] = sanitized_list[:nb_assets] if nb_assets else sanitized_list
+        final_list = sanitized_list[:nb_assets] if nb_assets else sanitized_list
+        _CONF['exchange']['pair_whitelist'] = final_list
 
         # Query trades from persistence layer
         trades = Trade.query.filter(Trade.is_open.is_(True)).all()
diff --git a/freqtrade/tests/test_acl_pair.py b/freqtrade/tests/test_acl_pair.py
index 33bfa7d0e..a37113ae0 100644
--- a/freqtrade/tests/test_acl_pair.py
+++ b/freqtrade/tests/test_acl_pair.py
@@ -52,7 +52,6 @@ def test_refresh_whitelist(mocker):
     print(conf['exchange']['pair_whitelist'])
     print(refreshedwhitelist)
     whitelist = ['BTC_ETH', 'BTC_TKN']
-    pairslist = conf['exchange']['pair_whitelist']
     # Ensure all except those in whitelist are removed
     assert_list_equal(whitelist, refreshedwhitelist)
 
diff --git a/freqtrade/tests/test_main.py b/freqtrade/tests/test_main.py
index a8d8c328c..605ac084b 100644
--- a/freqtrade/tests/test_main.py
+++ b/freqtrade/tests/test_main.py
@@ -179,6 +179,7 @@ def test_create_trade_no_pairs(default_conf, ticker, mocker):
         mocker.patch.dict('freqtrade.main._CONF', conf)
         create_trade(default_conf['stake_amount'])
 
+
 def test_create_trade_no_pairs_after_blacklist(default_conf, ticker, mocker):
     mocker.patch.dict('freqtrade.main._CONF', default_conf)
     mocker.patch('freqtrade.main.get_signal', side_effect=lambda s, t: True)