Placing any sign with setblock and a data tag crashes server

Note: Not tested on single player
When placing a sign with /setblock and a data tag crashes the server with message:

Internal Exception: io.netty.handler.codec.DecoderException: com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1