diff --git a/outlinecaddy/app.go b/outlinecaddy/app.go
index 73c51a95..fa4b8d7d 100644
--- a/outlinecaddy/app.go
+++ b/outlinecaddy/app.go
@@ -21,6 +21,7 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"strings"
 
 	outline_prometheus "github.com/Jigsaw-Code/outline-ss-server/prometheus"
 	outline "github.com/Jigsaw-Code/outline-ss-server/service"
@@ -127,7 +128,8 @@ func (app *OutlineApp) defineMetrics() error {
 func registerCollector[T prometheus.Collector](registerer prometheus.Registerer, coll T) (T, error) {
 	if err := registerer.Register(coll); err != nil {
 		are := &prometheus.AlreadyRegisteredError{}
-		if !errors.As(err, are) {
+		dupeErr := strings.Contains(err.Error(), "duplicate metrics collector registration attempted")
+		if !errors.As(err, are) || dupeErr {
 			// This collector has been registered before. This is expected during a config reload.
 			coll = are.ExistingCollector.(T)
 		} else {
diff --git a/service/shadowsocks.go b/service/shadowsocks.go
index 75bfe245..668da1c8 100644
--- a/service/shadowsocks.go
+++ b/service/shadowsocks.go
@@ -63,9 +63,17 @@ func NewShadowsocksHandlers(opts ...Option) (StreamHandler, AssociationHandler)
 		opt(s)
 	}
 
+	var (
+		tcpShadowsocksConnMetrics ShadowsocksConnMetrics
+		udpShadowsocksConnMetrics ShadowsocksConnMetrics
+	)
+	if s.metrics != nil {
+		tcpShadowsocksConnMetrics = &ssConnMetrics{s.metrics.AddTCPCipherSearch}
+		udpShadowsocksConnMetrics = &ssConnMetrics{s.metrics.AddUDPCipherSearch}
+	}
 	// TODO: Register initial data metrics at zero.
 	sh := NewStreamHandler(
-		NewShadowsocksStreamAuthenticator(s.ciphers, s.replayCache, &ssConnMetrics{s.metrics.AddTCPCipherSearch}, s.logger),
+		NewShadowsocksStreamAuthenticator(s.ciphers, s.replayCache, tcpShadowsocksConnMetrics, s.logger),
 		tcpReadTimeout,
 	)
 	if s.streamDialer != nil {
@@ -73,7 +81,7 @@ func NewShadowsocksHandlers(opts ...Option) (StreamHandler, AssociationHandler)
 	}
 	sh.SetLogger(s.logger)
 
-	ah := NewAssociationHandler(s.ciphers, &ssConnMetrics{s.metrics.AddUDPCipherSearch})
+	ah := NewAssociationHandler(s.ciphers, udpShadowsocksConnMetrics)
 	if s.packetListener != nil {
 		ah.SetTargetPacketListener(s.packetListener)
 	}