During the parameter replacement in @Query annotated repository methods previous versions wrote the String "null" into the query that was sent to Elasticsearch when the actual parameter value was null. As Elasticsearch does not store null values, this behaviour could lead to problems, for example whent the fields to be searched contains the string "null". In Version 5.3 a null value in a parameter will cause a ConversionException to be thrown. If you are using "null" as the null_value defined in a field mapping, then pass that string into the query instead of a Java null.spring-doc.cn