diff --git a/private/minis-backend/src/main/kotlin/de/walamana/models/Ministranten.kt b/private/minis-backend/src/main/kotlin/de/walamana/models/Ministranten.kt
index 25cbec5..97b06a6 100644
--- a/private/minis-backend/src/main/kotlin/de/walamana/models/Ministranten.kt
+++ b/private/minis-backend/src/main/kotlin/de/walamana/models/Ministranten.kt
@@ -20,7 +20,7 @@ data class Ministrant(
     val passwordHash: String? = "",
     val firstname: String,
     val lastname: String,
-    val birthday: DateAsLong,
+    val birthday: DateAsLong? = null,
     val privileges: CommaSeperatedStringList
 )
 
@@ -38,7 +38,7 @@ object Ministranten : Table() {
     val passwordHash = varchar("passwordHash", 1024)
     val firstname = varchar("firstname", 128)
     val lastname = varchar("lastname", 128)
-    val birthday = long("birthday")
+    val birthday = long("birthday").nullable()
     val privileges = varchar("privileges", 1024)
 
     override val primaryKey = PrimaryKey(id)
@@ -51,7 +51,7 @@ object MinistrantenDao {
         if (showPasswordHash) row[Ministranten.passwordHash] else "",
         row[Ministranten.firstname],
         row[Ministranten.lastname],
-        Date(row[Ministranten.birthday]),
+        row[Ministranten.birthday]?.let(::Date),
         row[Ministranten.privileges].split(",")
     )
 
@@ -96,7 +96,7 @@ object MinistrantenDao {
         passwordHash: String,
         firstname: String,
         lastname: String,
-        birthday: Date,
+        birthday: Date?,
         privileges: List<String>
     ) = dbQuery {
         val statement = Ministranten.insert {
@@ -104,7 +104,7 @@ object MinistrantenDao {
             it[Ministranten.passwordHash] = ""
             it[Ministranten.firstname] = firstname
             it[Ministranten.lastname] = lastname
-            it[Ministranten.birthday] = birthday.time
+            it[Ministranten.birthday] = birthday?.time
             it[Ministranten.privileges] = privileges.joinToString(",")
         }
         Security.setPassword(username, passwordHash)
diff --git a/private/minis-backend/src/main/kotlin/de/walamana/plugins/Databases.kt b/private/minis-backend/src/main/kotlin/de/walamana/plugins/Databases.kt
index 65fb568..a0a4d2e 100644
--- a/private/minis-backend/src/main/kotlin/de/walamana/plugins/Databases.kt
+++ b/private/minis-backend/src/main/kotlin/de/walamana/plugins/Databases.kt
@@ -29,6 +29,7 @@ fun Application.configureDatabases() {
         SchemaUtils.create(GottesdienstGroups)
         SchemaUtils.create(Gottesdienste)
         SchemaUtils.create(Marks)
+        exec("ALTER TABLE MINISTRANTEN ALTER COLUMN birthday BIGINT NULL;")
     }
 }