diff --git a/internal/cmd/flag.go b/internal/cmd/flag.go
index 42626d9f1..61e44d132 100644
--- a/internal/cmd/flag.go
+++ b/internal/cmd/flag.go
@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"strconv"
 	"strings"
+
+	"github.com/AdguardTeam/golibs/stringutil"
 )
 
 // uint32Value is an uint32 that can be defined as a flag for [flag.FlagSet].
@@ -65,8 +67,9 @@ type intSliceValue struct {
 	// values is the pointer to a slice of integers to store parsed values.
 	values *[]int
 
-	// wiped indicates if the default value has been overwritten.
-	wiped bool
+	// isSet is false until the corresponding flag is met for the first time.
+	// When the flag is found, the default value is overwritten with zero value.
+	isSet bool
 }
 
 // newIntSliceValue returns a pointer to intSliceValue with the given value.
@@ -75,7 +78,7 @@ func newIntSliceValue(val []int, p *[]int) (out *intSliceValue) {
 
 	return &intSliceValue{
 		values: p,
-		wiped:  false,
+		isSet:  false,
 	}
 }
 
@@ -93,8 +96,8 @@ func (i *intSliceValue) Set(s string) (err error) {
 			return fmt.Errorf("parsing integer slice arg %q: %w", s, err)
 		}
 
-		if !i.wiped {
-			i.wiped = true
+		if !i.isSet {
+			i.isSet = true
 			*i.values = []int{}
 		}
 
@@ -106,15 +109,16 @@ func (i *intSliceValue) Set(s string) (err error) {
 
 // String implements the [flag.Value] interface for *intSliceValue.
 func (i *intSliceValue) String() (out string) {
-	for _, v := range *i.values {
-		if len(out) > 0 {
-			out += ","
+	sb := &strings.Builder{}
+	for idx, v := range *i.values {
+		if idx > 0 {
+			stringutil.WriteToBuilder(sb, ",")
 		}
 
-		out += strconv.Itoa(v)
+		stringutil.WriteToBuilder(sb, strconv.Itoa(v))
 	}
 
-	return out
+	return sb.String()
 }
 
 // stringSliceValue represent a struct with a slice of strings that can be
@@ -123,8 +127,9 @@ type stringSliceValue struct {
 	// values is the pointer to a slice of string to store parsed values.
 	values *[]string
 
-	// wiped indicates if the default value has been overwritten.
-	wiped bool
+	// isSet is false until the corresponding flag is met for the first time.
+	// When the flag is found, the default value is overwritten with zero value.
+	isSet bool
 }
 
 // newStringSliceValue returns a pointer to stringSliceValue with the given
@@ -134,7 +139,7 @@ func newStringSliceValue(val []string, p *[]string) (out *stringSliceValue) {
 
 	return &stringSliceValue{
 		values: p,
-		wiped:  false,
+		isSet:  false,
 	}
 }
 
@@ -143,8 +148,8 @@ var _ flag.Value = (*stringSliceValue)(nil)
 
 // Set implements the [flag.Value] interface for *stringSliceValue.
 func (i *stringSliceValue) Set(s string) (err error) {
-	if !i.wiped {
-		i.wiped = true
+	if !i.isSet {
+		i.isSet = true
 		*i.values = []string{}
 	}
 
@@ -155,5 +160,14 @@ func (i *stringSliceValue) Set(s string) (err error) {
 
 // String implements the [flag.Value] interface for *stringSliceValue.
 func (i *stringSliceValue) String() (out string) {
-	return fmt.Sprintf("%s", *i.values)
+	sb := &strings.Builder{}
+	for idx, v := range *i.values {
+		if idx > 0 {
+			stringutil.WriteToBuilder(sb, ",")
+		}
+
+		stringutil.WriteToBuilder(sb, v)
+	}
+
+	return sb.String()
 }