diff --git a/metric/drpc.go b/metric/drpc.go
index b81ed863..23640a8c 100644
--- a/metric/drpc.go
+++ b/metric/drpc.go
@@ -2,8 +2,10 @@ package metric
 
 import (
 	"github.com/prometheus/client_golang/prometheus"
+	"go.uber.org/zap"
 	"storj.io/drpc"
 	"time"
+	"unicode/utf8"
 )
 
 type prometheusDRPC struct {
@@ -14,7 +16,11 @@ type prometheusDRPC struct {
 func (ph *prometheusDRPC) HandleRPC(stream drpc.Stream, rpc string) (err error) {
 	st := time.Now()
 	defer func() {
-		ph.SummaryVec.WithLabelValues(rpc).Observe(time.Since(st).Seconds())
+		if utf8.ValidString(rpc) {
+			ph.SummaryVec.WithLabelValues(rpc).Observe(time.Since(st).Seconds())
+		} else {
+			log.WarnCtx(stream.Context(), "invalid rpc string", zap.String("rpc", rpc))
+		}
 	}()
 	return ph.Handler.HandleRPC(stream, rpc)
 }