diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/enum_class.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/enum_class.mustache
index 9dbc1a250a02..65dfa1de08ba 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/enum_class.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/enum_class.mustache
@@ -18,10 +18,23 @@ import kotlinx.serialization.Serializable
 {{#enumUnknownDefaultCase}}
 import kotlinx.serialization.KSerializer
 import kotlinx.serialization.Serializer
+{{^isString}}
+import kotlinx.serialization.descriptors.PrimitiveKind
+import kotlinx.serialization.descriptors.PrimitiveSerialDescriptor
+{{/isString}}
 import kotlinx.serialization.builtins.serializer
 import kotlinx.serialization.encoding.Decoder
 import kotlinx.serialization.encoding.Encoder
 {{/enumUnknownDefaultCase}}
+{{^enumUnknownDefaultCase}}{{^isString}}
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.Serializer
+import kotlinx.serialization.descriptors.PrimitiveKind
+import kotlinx.serialization.descriptors.PrimitiveSerialDescriptor
+import kotlinx.serialization.builtins.serializer
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+{{/isString}}{{/enumUnknownDefaultCase}}
 {{/kotlinx_serialization}}
 {{/multiplatform}}
 {{#multiplatform}}
@@ -33,7 +46,7 @@ import kotlinx.serialization.*
  *
  * Values: {{#allowableValues}}{{#enumVars}}{{&name}}{{^-last}},{{/-last}}{{/enumVars}}{{/allowableValues}}
  */
-{{#multiplatform}}@Serializable{{/multiplatform}}{{#kotlinx_serialization}}@Serializable{{#enumUnknownDefaultCase}}(with = {{classname}}Serializer::class){{/enumUnknownDefaultCase}}{{/kotlinx_serialization}}
+{{#multiplatform}}@Serializable{{/multiplatform}}{{#kotlinx_serialization}}@Serializable{{#enumUnknownDefaultCase}}(with = {{classname}}Serializer::class){{/enumUnknownDefaultCase}}{{^enumUnknownDefaultCase}}{{^isString}}(with = {{classname}}Serializer::class){{/isString}}{{/enumUnknownDefaultCase}}{{/kotlinx_serialization}}
 {{^multiplatform}}
 {{#moshi}}
 @JsonClass(generateAdapter = false)
@@ -51,9 +64,9 @@ import kotlinx.serialization.*
     {{#jackson}}
     @JsonProperty(value = {{#lambda.doublequote}}{{{value}}}{{/lambda.doublequote}}){{#enumUnknownDefaultCase}}{{#-last}} @JsonEnumDefaultValue{{/-last}}{{/enumUnknownDefaultCase}}
     {{/jackson}}
-    {{#kotlinx_serialization}}
+    {{#kotlinx_serialization}}{{#isString}}
     @SerialName(value = {{#lambda.doublequote}}{{{value}}}{{/lambda.doublequote}})
-    {{/kotlinx_serialization}}
+    {{/isString}}{{/kotlinx_serialization}}
     {{/multiplatform}}
     {{#multiplatform}}
     @SerialName(value = {{#lambda.doublequote}}{{{value}}}{{/lambda.doublequote}})
@@ -95,18 +108,40 @@ import kotlinx.serialization.*
           }
         }
     }
-}{{#kotlinx_serialization}}{{#enumUnknownDefaultCase}}
-
+}
+{{#kotlinx_serialization}}{{#enumUnknownDefaultCase}}
 internal object {{classname}}Serializer : KSerializer<{{classname}}> {
-    override val descriptor = {{{dataType}}}.serializer().descriptor
+    override val descriptor = {{dataType}}.serializer().descriptor
 
     override fun deserialize(decoder: Decoder): {{classname}} {
         val value = decoder.decodeSerializableValue({{{dataType}}}.serializer())
         return {{classname}}.values().firstOrNull { it.value == value }
+            {{#isString}}
             ?: {{classname}}.{{#allowableValues}}{{#enumVars}}{{#-last}}{{&name}}{{/-last}}{{/enumVars}}{{/allowableValues}}
+            {{/isString}}
+            {{^isString}}
+            ?: throw IllegalArgumentException("Unknown enum value: $value")
+            {{/isString}}
+    }
+
+    override fun serialize(encoder: Encoder, value: {{classname}}) {
+        encoder.encodeSerializableValue({{{dataType}}}.serializer(), value.value)
+    }
+}
+{{/enumUnknownDefaultCase}}
+{{^enumUnknownDefaultCase}}{{^isString}}
+internal object {{classname}}Serializer : KSerializer<{{classname}}> {
+    override val descriptor = {{dataType}}.serializer().descriptor
+
+    override fun deserialize(decoder: Decoder): {{classname}} {
+        val value = decoder.decodeSerializableValue({{{dataType}}}.serializer())
+        return {{classname}}.values().firstOrNull { it.value == value }
+            ?: throw IllegalArgumentException("Unknown enum value: $value")
     }
 
     override fun serialize(encoder: Encoder, value: {{classname}}) {
         encoder.encodeSerializableValue({{{dataType}}}.serializer(), value.value)
     }
-}{{/enumUnknownDefaultCase}}{{/kotlinx_serialization}}
+}
+{{/isString}}{{/enumUnknownDefaultCase}}
+{{/kotlinx_serialization}}
\ No newline at end of file
diff --git a/samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/models/ApiStringEnumRef.kt b/samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/models/ApiStringEnumRef.kt
index 865fba881ff6..007c4017f056 100644
--- a/samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/models/ApiStringEnumRef.kt
+++ b/samples/client/echo_api/kotlin-jvm-okhttp/src/main/kotlin/org/openapitools/client/models/ApiStringEnumRef.kt
@@ -29,12 +29,15 @@ import com.squareup.moshi.JsonClass
 enum class ApiStringEnumRef(val value: kotlin.String) {
 
     @Json(name = "success")
+    
     success("success"),
 
     @Json(name = "failure")
+    
     failure("failure"),
 
     @Json(name = "unclassified")
+    
     unclassified("unclassified");
 
     /**
diff --git a/samples/client/echo_api/kotlin-jvm-spring-3-restclient/src/main/kotlin/org/openapitools/client/models/StringEnumRef.kt b/samples/client/echo_api/kotlin-jvm-spring-3-restclient/src/main/kotlin/org/openapitools/client/models/StringEnumRef.kt
index 93e12dd2ad7c..382563d3a1ba 100644
--- a/samples/client/echo_api/kotlin-jvm-spring-3-restclient/src/main/kotlin/org/openapitools/client/models/StringEnumRef.kt
+++ b/samples/client/echo_api/kotlin-jvm-spring-3-restclient/src/main/kotlin/org/openapitools/client/models/StringEnumRef.kt
@@ -28,15 +28,19 @@ import com.fasterxml.jackson.annotation.JsonProperty
 enum class StringEnumRef(val value: kotlin.String) {
 
     @JsonProperty(value = "success")
+    
     success("success"),
 
     @JsonProperty(value = "failure")
+    
     failure("failure"),
 
     @JsonProperty(value = "unclassified")
+    
     unclassified("unclassified"),
 
     @JsonProperty(value = "unknown_default_open_api") @JsonEnumDefaultValue
+    
     unknown_default_open_api("unknown_default_open_api");
 
     /**
diff --git a/samples/client/echo_api/kotlin-jvm-spring-3-webclient/src/main/kotlin/org/openapitools/client/models/StringEnumRef.kt b/samples/client/echo_api/kotlin-jvm-spring-3-webclient/src/main/kotlin/org/openapitools/client/models/StringEnumRef.kt
index 93e12dd2ad7c..382563d3a1ba 100644
--- a/samples/client/echo_api/kotlin-jvm-spring-3-webclient/src/main/kotlin/org/openapitools/client/models/StringEnumRef.kt
+++ b/samples/client/echo_api/kotlin-jvm-spring-3-webclient/src/main/kotlin/org/openapitools/client/models/StringEnumRef.kt
@@ -28,15 +28,19 @@ import com.fasterxml.jackson.annotation.JsonProperty
 enum class StringEnumRef(val value: kotlin.String) {
 
     @JsonProperty(value = "success")
+    
     success("success"),
 
     @JsonProperty(value = "failure")
+    
     failure("failure"),
 
     @JsonProperty(value = "unclassified")
+    
     unclassified("unclassified"),
 
     @JsonProperty(value = "unknown_default_open_api") @JsonEnumDefaultValue
+    
     unknown_default_open_api("unknown_default_open_api");
 
     /**
diff --git a/samples/client/echo_api/kotlin-model-prefix-type-mappings/src/main/kotlin/org/openapitools/client/models/ApiStringEnumRef.kt b/samples/client/echo_api/kotlin-model-prefix-type-mappings/src/main/kotlin/org/openapitools/client/models/ApiStringEnumRef.kt
index d9971985a7ea..ecb1ac4f48e7 100644
--- a/samples/client/echo_api/kotlin-model-prefix-type-mappings/src/main/kotlin/org/openapitools/client/models/ApiStringEnumRef.kt
+++ b/samples/client/echo_api/kotlin-model-prefix-type-mappings/src/main/kotlin/org/openapitools/client/models/ApiStringEnumRef.kt
@@ -27,12 +27,15 @@ import com.google.gson.annotations.SerializedName
 enum class ApiStringEnumRef(val value: kotlin.String) {
 
     @SerializedName(value = "success")
+    
     SUCCESS("success"),
 
     @SerializedName(value = "failure")
+    
     FAILURE("failure"),
 
     @SerializedName(value = "unclassified")
+    
     UNCLASSIFIED("unclassified");
 
     /**
diff --git a/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/models/PetEnum.kt b/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/models/PetEnum.kt
index 044b1b73ae23..98e4d2781484 100644
--- a/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/models/PetEnum.kt
+++ b/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/models/PetEnum.kt
@@ -24,6 +24,7 @@ import kotlinx.serialization.builtins.serializer
 import kotlinx.serialization.encoding.Decoder
 import kotlinx.serialization.encoding.Encoder
 
+
 /**
  * An enum with complex-ish naming
  *
@@ -32,13 +33,19 @@ import kotlinx.serialization.encoding.Encoder
 @Serializable(with = PetEnumSerializer::class)
 enum class PetEnum(val value: kotlin.String) {
 
+    
     @SerialName(value = "myFirstValue")
+    
     MY_FIRST_VALUE("myFirstValue"),
 
+    
     @SerialName(value = "MY_SECOND_VALUE")
+    
     MY_SECOND_VALUE("MY_SECOND_VALUE"),
 
+    
     @SerialName(value = "unknown_default_open_api")
+    
     UNKNOWN_DEFAULT_OPEN_API("unknown_default_open_api");
 
     /**
@@ -82,3 +89,4 @@ internal object PetEnumSerializer : KSerializer<PetEnum> {
     }
 }
 
+