The IPv4 pattern was used for IPv6

app/src/main/java/com/frostnerd/dnschanger/util/Preferences.java

@@ -40,7 +40,7 @@ public class Preferences extends com.frostnerd.utils.preferences.Preferences {
         builder.key("dns1-v6").ofType(Type.STRING).shouldNotBe(null).always().shouldNotBe("").always().shouldBeLike(Util.ipv6WithPort).always().doneWithKey();
         builder.key("dns2").ofType(Type.STRING).shouldNotBe(null).always().shouldBeLike(Util.ipv4WithPort)
                 .whenToStringIsNotEmpty().doneWithKey();
-        builder.key("dns2-v6").ofType(Type.STRING).shouldNotBe(null).always().shouldBeLike(Util.ipv4WithPort)
+        builder.key("dns2-v6").ofType(Type.STRING).shouldNotBe(null).always().shouldBeLike(Util.ipv6WithPort)
                 .whenToStringIsNotEmpty().doneWithKey();
 
         builder.key("setting_ipv6_enabled").ofType(Type.BOOLEAN).shouldNotBe(false).when(new PreferenceRestriction.Condition() {