I'm hitting 'org.hibernate.AnnotationException: Mixing nullable and non nullable columns in a property is not allowed' when using hibernate generated entities

Issue

• I'm generating entities from a table having a primary key based on many columns. Once hibernate starts with such generated Entities, following error is raised

  org.hibernate.AnnotationException: Mixing nullable and non nullable columns in a property is not allowed: org.domain.project.entity.Employeetask
   at org.hibernate.cfg.Ejb3Column.checkPropertyConsistency(Ejb3Column.java:414)
   at org.hibernate.cfg.AnnotationBinder.bindManyToOne(AnnotationBinder.java:1981)
   at org.hibernate.cfg.AnnotationBinder.processElementAnnotations(AnnotationBinder.java:1361)
   at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:754)
   at org.hibernate.cfg.AnnotationConfiguration.processArtifactsOfType(AnnotationConfiguration.java:546)
   at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:291)