diff --git a/src/main/kotlin/fr/postgresjson/entity/immutable/ImmutableEntity.kt b/src/main/kotlin/fr/postgresjson/entity/immutable/ImmutableEntity.kt
index 6ed1324..b4849b4 100644
--- a/src/main/kotlin/fr/postgresjson/entity/immutable/ImmutableEntity.kt
+++ b/src/main/kotlin/fr/postgresjson/entity/immutable/ImmutableEntity.kt
@@ -21,14 +21,14 @@ open class UuidEntity(override val id: UUID = UUID.randomUUID()) : UuidEntityI,
 
 /* Version */
 interface EntityVersioning<ID, NUMBER> {
-    val versionId: ID
     val versionNumber: NUMBER
+    val versionId: ID
 }
 
 class UuidEntityVersioning(
-    override val versionNumber: Int,
+    override var versionNumber: Int? = null,
     override val versionId: UUID = UUID.randomUUID()
-) : EntityVersioning<UUID, Int>
+) : EntityVersioning<UUID, Int?>
 
 /* Dates */
 interface EntityCreatedAt {
diff --git a/src/main/kotlin/fr/postgresjson/entity/mutable/MutableEntity.kt b/src/main/kotlin/fr/postgresjson/entity/mutable/MutableEntity.kt
index 96f5145..d2b8949 100644
--- a/src/main/kotlin/fr/postgresjson/entity/mutable/MutableEntity.kt
+++ b/src/main/kotlin/fr/postgresjson/entity/mutable/MutableEntity.kt
@@ -26,10 +26,10 @@ interface EntityVersioning<ID, NUMBER> {
     var versionNumber: NUMBER?
 }
 
-class UuidEntityVersioning : EntityVersioning<UUID, Int> {
+class UuidEntityVersioning(
+    override var versionNumber: Int? = null,
     override var versionId: UUID = UUID.randomUUID()
-    override var versionNumber: Int? = null
-}
+): EntityVersioning<UUID, Int>
 
 /* Dates */
 interface EntityCreatedAt {