Error in Java: Cloud Functions - hello-pubsub

[meteatamel]

Ends up with this error sometimes:

Failed to execute functions.Function
com.google.protobuf.InvalidProtocolBufferException: Field google.events.cloud.pubsub.v1.PubsubMessage.message_id has already been set.
at com.google.protobuf.util.JsonFormat$ParserImpl.mergeField(JsonFormat.java:1647)
at com.google.protobuf.util.JsonFormat$ParserImpl.mergeMessage(JsonFormat.java:1493)
at com.google.protobuf.util.JsonFormat$ParserImpl.merge(JsonFormat.java:1451)
at com.google.protobuf.util.JsonFormat$ParserImpl.parseFieldValue(JsonFormat.java:2011)
at com.google.protobuf.util.JsonFormat$ParserImpl.mergeField(JsonFormat.java:1662)
at com.google.protobuf.util.JsonFormat$ParserImpl.mergeMessage(JsonFormat.java:1493)
at com.google.protobuf.util.JsonFormat$ParserImpl.merge(JsonFormat.java:1451)
at com.google.protobuf.util.JsonFormat$ParserImpl.merge(JsonFormat.java:1333)
at com.google.protobuf.util.JsonFormat$Parser.merge(JsonFormat.java:473)
at functions.Function.accept(Function.java:40)
at com.google.cloud.functions.invoker.BackgroundFunctionExecutor$CloudEventFunctionExecutor.serviceCloudEvent(BackgroundFunctionExecutor.java:317)
at com.google.cloud.functions.invoker.BackgroundFunctionExecutor.lambda$serviceCloudEvent$6(BackgroundFunctionExecutor.java:362)
at com.google.cloud.functions.invoker.BackgroundFunctionExecutor.runWithContextClassLoader(BackgroundFunctionExecutor.java:386)
at com.google.cloud.functions.invoker.BackgroundFunctionExecutor.serviceCloudEvent(BackgroundFunctionExecutor.java:362)
at com.google.cloud.functions.invoker.BackgroundFunctionExecutor.service(BackgroundFunctionExecutor.java:328)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:755)