Int / Float cannot be decoded

I am currently using a JSON library that is encoding 0 for a double to "0" instead of "0.0", without the quotes. First, I feel that "0" is a perfectly valid value for 0 as a double. But, I tried to code around it by changing the "type" of the field to "["double", "int"]", without the quotes and it is giving me this error:

Exception in thread "main" org.apache.avro.AvroTypeException: Expected start-union. Got VALUE_NUMBER_INT
at org.apache.avro.io.JsonDecoder.error(JsonDecoder.java:697)
at org.apache.avro.io.JsonDecoder.readIndex(JsonDecoder.java:441)
at org.apache.avro.io.ResolvingDecoder.doAction(ResolvingDecoder.java:229)
at org.apache.avro.io.parsing.Parser.advance(Parser.java:88)
at org.apache.avro.io.ResolvingDecoder.readIndex(ResolvingDecoder.java:206)
at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:148)
at org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:173)
at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:144)
at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:135)

If I change it to just "int", then it works for a few records until it reaches a double.

Thank you,

John