Failed to send one byte message to AWS IOT Wireless device through queue downlink message

When I try to send a one byte message to my LoRa device that is connected to AWS IOT Wireless server I get a warning when I enter "1" in the Payload field and try to Submit that says:

Payload must follow pattern: ^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$

This is under: AWS IoT > Wireless connectivity > Wireless devices > [Device ID] > Queue downlink message