diff --git a/pkg/core/tradecollector.go b/pkg/core/tradecollector.go
index 9622e912c..ed581704f 100644
--- a/pkg/core/tradecollector.go
+++ b/pkg/core/tradecollector.go
@@ -32,9 +32,11 @@ func (s *ConverterSetting) InitializeConverter() (Converter, error) {
 
 	logrus.Infof("initializing converter %T ...", converter)
 	err := converter.Initialize()
-	return nil, err
+	return converter, err
 }
 
+// ConverterManager manages the converters for trade conversion
+// It can be used to convert the trade symbol into the target symbol, or convert the price, volume into different units.
 type ConverterManager struct {
 	ConverterSettings []ConverterSetting `json:"converters,omitempty" yaml:"converters,omitempty"`
 
@@ -43,15 +45,18 @@ type ConverterManager struct {
 
 func (c *ConverterManager) Initialize() error {
 	for _, setting := range c.ConverterSettings {
-
 		converter, err := setting.InitializeConverter()
 		if err != nil {
 			return err
 		}
 
-		c.AddConverter(converter)
+		if converter != nil {
+			c.AddConverter(converter)
+		}
 	}
 
+	numConverters := len(c.converters)
+	logrus.Infof("%d converters loaded", numConverters)
 	return nil
 }
 
diff --git a/pkg/core/tradecollector_test.go b/pkg/core/tradecollector_test.go
index 0b1f8772f..8f9ccf841 100644
--- a/pkg/core/tradecollector_test.go
+++ b/pkg/core/tradecollector_test.go
@@ -9,6 +9,28 @@ import (
 	"github.com/c9s/bbgo/pkg/types"
 )
 
+func TestTradeCollector_NilConvertManager(t *testing.T) {
+	symbol := "BTCUSDT"
+	position := types.NewPosition(symbol, "BTC", "USDT")
+	orderStore := NewOrderStore(symbol)
+	collector := NewTradeCollector(symbol, position, orderStore)
+
+	trade := types.Trade{
+		ID:            1,
+		OrderID:       399,
+		Exchange:      types.ExchangeBinance,
+		Price:         fixedpoint.NewFromInt(40000),
+		Quantity:      fixedpoint.One,
+		QuoteQuantity: fixedpoint.NewFromInt(40000),
+		Symbol:        "BTCUSDT",
+		Side:          types.SideTypeBuy,
+		IsBuyer:       true,
+	}
+
+	trade = collector.ConvertTrade(trade)
+	assert.Equal(t, "BTCUSDT", trade.Symbol)
+}
+
 func TestTradeCollector_ShouldNotCountDuplicatedTrade(t *testing.T) {
 	symbol := "BTCUSDT"
 	position := types.NewPosition(symbol, "BTC", "USDT")
diff --git a/pkg/types/position.go b/pkg/types/position.go
index d0b37f031..2d71ee740 100644
--- a/pkg/types/position.go
+++ b/pkg/types/position.go
@@ -190,6 +190,7 @@ func (p *Position) NewMarketCloseOrder(percentage fixedpoint.Value) *SubmitOrder
 	}
 }
 
+// IsDust checks if the position is dust, the first argument is the price to calculate the dust quantity
 func (p *Position) IsDust(a ...fixedpoint.Value) bool {
 	price := p.AverageCost
 	if len(a) > 0 {
@@ -448,6 +449,7 @@ func (p *Position) String() string {
 	)
 }
 
+// BindStream binds the trade update callback and update the position
 func (p *Position) BindStream(stream Stream) {
 	stream.OnTradeUpdate(func(trade Trade) {
 		if p.Symbol == trade.Symbol {
@@ -540,7 +542,7 @@ func (p *Position) AddTrade(td Trade) (profit fixedpoint.Value, netProfit fixedp
 	p.addTradeFee(td)
 
 	// Base > 0 means we're in long position
-	// Base < 0  means we're in short position
+	// Base < 0 means we're in short position
 	switch td.Side {
 
 	case SideTypeBuy: