diff --git a/freqtrade/optimize/backtesting.py b/freqtrade/optimize/backtesting.py
index c72a8b5c5..19ae74ae6 100644
--- a/freqtrade/optimize/backtesting.py
+++ b/freqtrade/optimize/backtesting.py
@@ -225,6 +225,22 @@ class Backtesting:
                 # sell at open price.
                 return sell_row[OPEN_IDX]
 
+            # Special case: trailing triggers within same candle as trade opened. Assume most
+            # pessimistic price movement, which is moving just enough to arm stoploss and
+            # immediately going down to stop price.
+            if sell.sell_type == SellType.TRAILING_STOP_LOSS and trade_dur == 0 and \
+               self.strategy.trailing_stop_positive:
+                if self.strategy.trailing_only_offset_is_reached:
+                    # Worst case: price reaches stop_positive_offset and dives down.
+                    stop_rate = sell_row[OPEN_IDX] * \
+                                (1 + abs(self.strategy.trailing_stop_positive_offset) -
+                                 abs(self.strategy.trailing_stop_positive))
+                else:
+                    # Worst case: price ticks tiny bit above open and dives down.
+                    stop_rate = sell_row[OPEN_IDX] * (1 - abs(self.strategy.trailing_stop_positive))
+                    assert stop_rate < sell_row[HIGH_IDX]
+                return stop_rate
+
             # Set close_rate to stoploss
             return trade.stop_loss
         elif sell.sell_type == (SellType.ROI):
diff --git a/freqtrade/strategy/interface.py b/freqtrade/strategy/interface.py
index 8ea38f503..47d4259fc 100644
--- a/freqtrade/strategy/interface.py
+++ b/freqtrade/strategy/interface.py
@@ -610,7 +610,7 @@ class IStrategy(ABC, HyperStrategyMixin):
         # Initiate stoploss with open_rate. Does nothing if stoploss is already set.
         trade.adjust_stop_loss(trade.open_rate, stop_loss_value, initial=True)
 
-        if self.use_custom_stoploss:
+        if self.use_custom_stoploss and trade.stop_loss < current_rate:
             stop_loss_value = strategy_safe_wrapper(self.custom_stoploss, default_retval=None
                                                     )(pair=trade.pair, trade=trade,
                                                       current_time=current_time,
@@ -623,7 +623,7 @@ class IStrategy(ABC, HyperStrategyMixin):
             else:
                 logger.warning("CustomStoploss function did not return valid stoploss")
 
-        if self.trailing_stop:
+        if self.trailing_stop and trade.stop_loss < current_rate:
             # trailing stoploss handling
             sl_offset = self.trailing_stop_positive_offset
 
diff --git a/tests/optimize/test_backtest_detail.py b/tests/optimize/test_backtest_detail.py
index e5b969383..488425323 100644
--- a/tests/optimize/test_backtest_detail.py
+++ b/tests/optimize/test_backtest_detail.py
@@ -457,6 +457,50 @@ tc28 = BTContainer(data=[
     trades=[BTrade(sell_reason=SellType.TRAILING_STOP_LOSS, open_tick=1, close_tick=3)]
 )
 
+# Test 29: trailing_stop should be triggered by low of next candle, without adjusting stoploss using
+# high of stoploss candle.
+# stop-loss: 10%, ROI: 10% (should not apply)
+tc29 = BTContainer(data=[
+    # D   O     H     L     C    V    B  S
+    [0, 5000, 5050, 4950, 5000, 6172, 1, 0],
+    [1, 5000, 5050, 5000, 4900, 6172, 0, 0],    # enter trade (signal on last candle)
+    [2, 4900, 5250, 4500, 5100, 6172, 0, 0],    # Triggers trailing-stoploss
+    [3, 5100, 5100, 4650, 4750, 6172, 0, 0],
+    [4, 4750, 4950, 4350, 4750, 6172, 0, 0]],
+    stop_loss=-0.10, roi={"0": 0.10}, profit_perc=-0.02, trailing_stop=True,
+    trailing_stop_positive=0.03,
+    trades=[BTrade(sell_reason=SellType.TRAILING_STOP_LOSS, open_tick=1, close_tick=2)]
+)
+
+# Test 30: trailing_stop should be triggered immediately on trade open candle.
+# stop-loss: 10%, ROI: 10% (should not apply)
+tc30 = BTContainer(data=[
+    # D   O     H     L     C    V    B  S
+    [0, 5000, 5050, 4950, 5000, 6172, 1, 0],
+    [1, 5000, 5500, 5000, 4900, 6172, 0, 0],    # enter trade (signal on last candle) and stop
+    [2, 4900, 5250, 4500, 5100, 6172, 0, 0],
+    [3, 5100, 5100, 4650, 4750, 6172, 0, 0],
+    [4, 4750, 4950, 4350, 4750, 6172, 0, 0]],
+    stop_loss=-0.10, roi={"0": 0.10}, profit_perc=-0.01, trailing_stop=True,
+    trailing_stop_positive=0.01,
+    trades=[BTrade(sell_reason=SellType.TRAILING_STOP_LOSS, open_tick=1, close_tick=1)]
+)
+
+# Test 31: trailing_stop should be triggered immediately on trade open candle.
+# stop-loss: 10%, ROI: 10% (should not apply)
+tc31 = BTContainer(data=[
+    # D   O     H     L     C    V    B  S
+    [0, 5000, 5050, 4950, 5000, 6172, 1, 0],
+    [1, 5000, 5500, 5000, 4900, 6172, 0, 0],    # enter trade (signal on last candle) and stop
+    [2, 4900, 5250, 4500, 5100, 6172, 0, 0],
+    [3, 5100, 5100, 4650, 4750, 6172, 0, 0],
+    [4, 4750, 4950, 4350, 4750, 6172, 0, 0]],
+    stop_loss=-0.10, roi={"0": 0.10}, profit_perc=0.01, trailing_stop=True,
+    trailing_only_offset_is_reached=True, trailing_stop_positive_offset=0.02,
+    trailing_stop_positive=0.01,
+    trades=[BTrade(sell_reason=SellType.TRAILING_STOP_LOSS, open_tick=1, close_tick=1)]
+)
+
 TESTS = [
     tc0,
     tc1,
@@ -487,6 +531,9 @@ TESTS = [
     tc26,
     tc27,
     tc28,
+    tc29,
+    tc30,
+    tc31,
 ]