diff --git a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Category.kt b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Category.kt
index 7647c2d227e0..9d8571921384 100644
--- a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Category.kt
+++ b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Category.kt
@@ -12,17 +12,19 @@
 package org.openapitools.server.models
 
 
-import kotlinx.serialization.Serializable
+import java.io.Serializable
 /**
  * A category for a pet
  * @param id 
  * @param name 
  */
-@Serializable
 data class Category(
     val id: kotlin.Long? = null,
     val name: kotlin.String? = null
-)
+) : Serializable 
 {
+    companion object {
+        private const val serialVersionUID: Long = 123
+    }
 }
 
diff --git a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
index e16d42e86a4e..5548175d9048 100644
--- a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
+++ b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
@@ -12,19 +12,21 @@
 package org.openapitools.server.models
 
 
-import kotlinx.serialization.Serializable
+import java.io.Serializable
 /**
  * Describes the result of uploading an image resource
  * @param code 
  * @param type 
  * @param message 
  */
-@Serializable
 data class ModelApiResponse(
     val code: kotlin.Int? = null,
     val type: kotlin.String? = null,
     val message: kotlin.String? = null
-)
+) : Serializable 
 {
+    companion object {
+        private const val serialVersionUID: Long = 123
+    }
 }
 
diff --git a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Order.kt b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Order.kt
index a75a759f7a93..79dce95e1e47 100644
--- a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Order.kt
+++ b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Order.kt
@@ -12,7 +12,7 @@
 package org.openapitools.server.models
 
 
-import kotlinx.serialization.Serializable
+import java.io.Serializable
 /**
  * An order for a pets from the pet store
  * @param id 
@@ -22,7 +22,6 @@ import kotlinx.serialization.Serializable
  * @param status Order Status
  * @param complete 
  */
-@Serializable
 data class Order(
     val id: kotlin.Long? = null,
     val petId: kotlin.Long? = null,
@@ -31,8 +30,11 @@ data class Order(
     /* Order Status */
     val status: Order.Status? = null,
     val complete: kotlin.Boolean? = false
-)
+) : Serializable 
 {
+    companion object {
+        private const val serialVersionUID: Long = 123
+    }
     /**
     * Order Status
     * Values: placed,approved,delivered
diff --git a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Pet.kt b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Pet.kt
index 8fe934cc3ff3..8b98ce0469c5 100644
--- a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Pet.kt
+++ b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Pet.kt
@@ -14,7 +14,7 @@ package org.openapitools.server.models
 import org.openapitools.server.models.Category
 import org.openapitools.server.models.Tag
 
-import kotlinx.serialization.Serializable
+import java.io.Serializable
 /**
  * A pet for sale in the pet store
  * @param name 
@@ -24,7 +24,6 @@ import kotlinx.serialization.Serializable
  * @param tags 
  * @param status pet status in the store
  */
-@Serializable
 data class Pet(
     val name: kotlin.String,
     val photoUrls: kotlin.collections.List<kotlin.String>,
@@ -33,8 +32,11 @@ data class Pet(
     val tags: kotlin.collections.List<Tag>? = null,
     /* pet status in the store */
     val status: Pet.Status? = null
-)
+) : Serializable 
 {
+    companion object {
+        private const val serialVersionUID: Long = 123
+    }
     /**
     * pet status in the store
     * Values: available,pending,sold
diff --git a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Tag.kt b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Tag.kt
index fae4d9d0ba3c..e9626b25c6d1 100644
--- a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Tag.kt
+++ b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/Tag.kt
@@ -12,17 +12,19 @@
 package org.openapitools.server.models
 
 
-import kotlinx.serialization.Serializable
+import java.io.Serializable
 /**
  * A tag for a pet
  * @param id 
  * @param name 
  */
-@Serializable
 data class Tag(
     val id: kotlin.Long? = null,
     val name: kotlin.String? = null
-)
+) : Serializable 
 {
+    companion object {
+        private const val serialVersionUID: Long = 123
+    }
 }
 
diff --git a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/User.kt b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/User.kt
index af04fd61c1cf..fdbdb4e1cff4 100644
--- a/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/User.kt
+++ b/samples/server/petstore/kotlin-server/ktor2/src/main/kotlin/org/openapitools/server/models/User.kt
@@ -12,7 +12,7 @@
 package org.openapitools.server.models
 
 
-import kotlinx.serialization.Serializable
+import java.io.Serializable
 /**
  * A User who is purchasing from the pet store
  * @param id 
@@ -24,7 +24,6 @@ import kotlinx.serialization.Serializable
  * @param phone 
  * @param userStatus User Status
  */
-@Serializable
 data class User(
     val id: kotlin.Long? = null,
     val username: kotlin.String? = null,
@@ -35,7 +34,10 @@ data class User(
     val phone: kotlin.String? = null,
     /* User Status */
     val userStatus: kotlin.Int? = null
-)
+) : Serializable 
 {
+    companion object {
+        private const val serialVersionUID: Long = 123
+    }
 }