diff --git a/cmd_string.go b/cmd_string.go
index 19c3543..985848c 100644
--- a/cmd_string.go
+++ b/cmd_string.go
@@ -4,6 +4,7 @@ package miniredis
 
 import (
 	"math/big"
+	"math/bits"
 	"strconv"
 	"strings"
 	"time"
@@ -1114,10 +1115,7 @@ func withRange(v string, start, end int) string {
 func countBits(v []byte) int {
 	count := 0
 	for _, b := range []byte(v) {
-		for b > 0 {
-			count += int((b % uint8(2)))
-			b = b >> 1
-		}
+		count += bits.OnesCount8(uint8(b))
 	}
 	return count
 }