diff --git a/src/main/kotlin/dev/usbharu/hideout/activitypub/domain/model/Undo.kt b/src/main/kotlin/dev/usbharu/hideout/activitypub/domain/model/Undo.kt
index 01dbc17c..b1399777 100644
--- a/src/main/kotlin/dev/usbharu/hideout/activitypub/domain/model/Undo.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/activitypub/domain/model/Undo.kt
@@ -1,5 +1,6 @@
 package dev.usbharu.hideout.activitypub.domain.model
 
+import com.fasterxml.jackson.annotation.JsonProperty
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize
 import dev.usbharu.hideout.activitypub.domain.model.objects.Object
 import dev.usbharu.hideout.activitypub.domain.model.objects.ObjectDeserializer
@@ -9,7 +10,7 @@ open class Undo(
     override val actor: String,
     override val id: String,
     @JsonDeserialize(using = ObjectDeserializer::class)
-    @Suppress("VariableNaming") val `object`: Object,
+    @JsonProperty("object") val apObject: Object,
     val published: String
 ) : Object(add(type, "Undo")), HasId, HasActor {
 
@@ -20,7 +21,7 @@ open class Undo(
 
         other as Undo
 
-        if (`object` != other.`object`) return false
+        if (apObject != other.apObject) return false
         if (published != other.published) return false
         if (actor != other.actor) return false
         if (id != other.id) return false
@@ -30,7 +31,7 @@ open class Undo(
 
     override fun hashCode(): Int {
         var result = super.hashCode()
-        result = 31 * result + `object`.hashCode()
+        result = 31 * result + apObject.hashCode()
         result = 31 * result + published.hashCode()
         result = 31 * result + actor.hashCode()
         result = 31 * result + id.hashCode()
@@ -38,5 +39,5 @@ open class Undo(
     }
 
     override fun toString(): String =
-        "Undo(`object`=$`object`, published=$published, actor='$actor', id='$id') ${super.toString()}"
+        "Undo(`object`=$apObject, published=$published, actor='$actor', id='$id') ${super.toString()}"
 }
diff --git a/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/like/ApRemoveReactionJobProcessor.kt b/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/like/ApRemoveReactionJobProcessor.kt
index 285670b5..0409b9a0 100644
--- a/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/like/ApRemoveReactionJobProcessor.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/like/ApRemoveReactionJobProcessor.kt
@@ -31,7 +31,7 @@ class ApRemoveReactionJobProcessor(
             param.inbox,
             Undo(
                 actor = param.actor,
-                `object` = like,
+                apObject = like,
                 id = "${applicationConfig.url}/undo/like/${param.id}",
                 published = Instant.now().toString()
             ),
diff --git a/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/undo/APSendUndoServiceImpl.kt b/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/undo/APSendUndoServiceImpl.kt
index 3945cc5a..e1d4c6fd 100644
--- a/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/undo/APSendUndoServiceImpl.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/undo/APSendUndoServiceImpl.kt
@@ -22,7 +22,7 @@ class APSendUndoServiceImpl(
             Undo(
                 actor = user.url,
                 id = "${applicationConfig.url}/undo/follow/${user.id}/${target.url}",
-                `object` = Follow(
+                apObject = Follow(
                     apObject = user.url,
                     actor = target.url
                 ),
@@ -40,7 +40,7 @@ class APSendUndoServiceImpl(
             Undo(
                 actor = user.url,
                 id = "${applicationConfig.url}/undo/block/${user.id}/${target.url}",
-                `object` = Block(
+                apObject = Block(
                     apObject = user.url,
                     actor = target.url,
                     id = "${applicationConfig.url}/block/${user.id}/${target.id}"
diff --git a/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/undo/APUndoProcessor.kt b/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/undo/APUndoProcessor.kt
index 6f44abc6..f6a3ff0e 100644
--- a/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/undo/APUndoProcessor.kt
+++ b/src/main/kotlin/dev/usbharu/hideout/activitypub/service/activity/undo/APUndoProcessor.kt
@@ -28,13 +28,13 @@ class APUndoProcessor(
         }
 
         val type =
-            undo.`object`.type.orEmpty()
+            undo.apObject.type.orEmpty()
                 .firstOrNull { it == "Block" || it == "Follow" || it == "Like" || it == "Announce" || it == "Accept" }
                 ?: return
 
         when (type) {
             "Follow" -> {
-                val follow = undo.`object` as Follow
+                val follow = undo.apObject as Follow
 
                 apUserService.fetchPerson(undo.actor, follow.apObject)
                 val follower = userQueryService.findByUrl(undo.actor)