diff --git a/arn/validate/Validate.go b/arn/validate/Validate.go
index 08492a88..94de54d1 100644
--- a/arn/validate/Validate.go
+++ b/arn/validate/Validate.go
@@ -5,6 +5,7 @@ import (
 	"regexp"
 	"strings"
 	"time"
+	"unicode/utf8"
 
 	"github.com/animenotifier/notify.moe/arn/autocorrect"
 )
@@ -31,6 +32,10 @@ func Nick(nick string) bool {
 		return false
 	}
 
+	if !utf8.ValidString(nick) {
+		return false
+	}
+
 	return nick == autocorrect.UserNick(nick)
 }
 
diff --git a/arn/validate/Validate_test.go b/arn/validate/Validate_test.go
index 33031f6b..b2ccadae 100644
--- a/arn/validate/Validate_test.go
+++ b/arn/validate/Validate_test.go
@@ -18,6 +18,7 @@ func TestIsValidNick(t *testing.T) {
 	assert.False(t, validate.Nick("Tsun.Dere"))
 	assert.False(t, validate.Nick("Tsun Dere"))
 	assert.False(t, validate.Nick("さとう"))
+	assert.False(t, validate.Nick(string([]byte{0xff, 0xfe, 0xfd})))
 
 	// Valid nicknames
 	assert.True(t, validate.Nick("Tsundere"))