It would be better if it raised an exception, then the user would be aware of the issue. Right now it silently drops the data. Imported from Jira [BEAM-7809](https://issues.apache.org/jira/browse/BEAM-7809). Original Jira may contain additional context. Reported by: ajamato@google.com.