Подгонка regexp к серверной валидации

app/views/Profile/MyProfile.tsx

@@ -100,7 +100,7 @@ export function MyProfile() {
                         onErrorStateChange={(error) => setUsernameError(error)}
                         placeholder="ex. freddie871"
                         onChange={(e) => setUsername(e.target.value)}
-                        regexp={new RegExp(/^([a-z0-9]{5,16})?$/)}
+                        regexp={new RegExp(/^([a-z][a-z0-9_]{4,15})?$/)}
                     ></SettingsInput.Default>
                 </SettingsInput.Group>
                 {usernameError && <Text c={'red'} fz={10} pl={'xs'} mt={3}>Invalid username.</Text>}