diff --git a/detekt.yml b/detekt.yml
index d0f97bdc..bf483322 100644
--- a/detekt.yml
+++ b/detekt.yml
@@ -92,7 +92,7 @@ exceptions:
     active: true
 
   NotImplementedDeclaration:
-    active: true
+    active: false
 
   ObjectExtendsThrowable:
     active: true
diff --git a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Accept.kt b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Accept.kt
index 487a31d6..e25d0e6d 100644
--- a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Accept.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Accept.kt
@@ -20,10 +20,7 @@ open class Accept : Object {
         this.`object` = `object`
     }
 
-
-    override fun toString(): String {
-        return "Accept(`object`=$`object`) ${super.toString()}"
-    }
+    override fun toString(): String = "Accept(`object`=$`object`) ${super.toString()}"
 
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
@@ -38,6 +35,4 @@ open class Accept : Object {
         result = 31 * result + (`object`?.hashCode() ?: 0)
         return result
     }
-
-
 }
diff --git a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Follow.kt b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Follow.kt
index cc7ae0e6..d15d7631 100644
--- a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Follow.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Follow.kt
@@ -31,9 +31,5 @@ open class Follow : Object {
         return result
     }
 
-    override fun toString(): String {
-        return "Follow(`object`=$`object`) ${super.toString()}"
-    }
-
-
+    override fun toString(): String = "Follow(`object`=$`object`) ${super.toString()}"
 }
diff --git a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/ObjectDeserializer.kt b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/ObjectDeserializer.kt
index c142d1f9..70bcee3b 100644
--- a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/ObjectDeserializer.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/ObjectDeserializer.kt
@@ -45,5 +45,4 @@ class ObjectDeserializer : JsonDeserializer<Object>() {
             TODO()
         }
     }
-
 }
diff --git a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/ObjectValue.kt b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/ObjectValue.kt
index 978e7db4..635d560d 100644
--- a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/ObjectValue.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/ObjectValue.kt
@@ -1,10 +1,10 @@
 package dev.usbharu.hideout.domain.model.ap
 
-class ObjectValue : Object {
+open class ObjectValue : Object {
 
     var `object`: String? = null
 
-    protected constructor()
+    protected constructor() : super()
     constructor(type: List<String>, name: String?, actor: String?, id: String?, `object`: String?) : super(
         type,
         name,
@@ -28,9 +28,5 @@ class ObjectValue : Object {
         return result
     }
 
-    override fun toString(): String {
-        return "ObjectValue(`object`=$`object`) ${super.toString()}"
-    }
-
-
+    override fun toString(): String = "ObjectValue(`object`=$`object`) ${super.toString()}"
 }
diff --git a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Undo.kt b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Undo.kt
index 804e5060..8a175f22 100644
--- a/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Undo.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/domain/model/ap/Undo.kt
@@ -3,13 +3,13 @@ package dev.usbharu.hideout.domain.model.ap
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize
 import java.time.Instant
 
-class Undo : Object {
+open class Undo : Object {
 
     @JsonDeserialize(using = ObjectDeserializer::class)
     var `object`: Object? = null
     var published: String? = null
 
-    protected constructor()
+    protected constructor() : super()
     constructor(
         type: List<String> = emptyList(),
         name: String,
@@ -38,9 +38,5 @@ class Undo : Object {
         return result
     }
 
-    override fun toString(): String {
-        return "Undo(`object`=$`object`, published=$published) ${super.toString()}"
-    }
-
-
+    override fun toString(): String = "Undo(`object`=$`object`, published=$published) ${super.toString()}"
 }
diff --git a/src/main/kotlin/dev/usbharu/hideout/service/activitypub/ActivityPubUndoServiceImpl.kt b/src/main/kotlin/dev/usbharu/hideout/service/activitypub/ActivityPubUndoServiceImpl.kt
index be826cc1..d8bf3e5d 100644
--- a/src/main/kotlin/dev/usbharu/hideout/service/activitypub/ActivityPubUndoServiceImpl.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/service/activitypub/ActivityPubUndoServiceImpl.kt
@@ -14,7 +14,6 @@ class ActivityPubUndoServiceImpl(
     private val activityPubUserService: ActivityPubUserService
 ) : ActivityPubUndoService {
     override suspend fun receiveUndo(undo: Undo): ActivityPubResponse {
-
         if (undo.actor == null) {
             return ActivityPubStringResponse(HttpStatusCode.BadRequest, "actor is null")
         }