diff --git a/src/main/kotlin/org/gitanimals/render/domain/AbstractTime.kt b/src/main/kotlin/org/gitanimals/render/domain/AbstractTime.kt
index 0b86180..85f6ec8 100644
--- a/src/main/kotlin/org/gitanimals/render/domain/AbstractTime.kt
+++ b/src/main/kotlin/org/gitanimals/render/domain/AbstractTime.kt
@@ -2,6 +2,7 @@ package org.gitanimals.render.domain
 
 import jakarta.persistence.Column
 import jakarta.persistence.MappedSuperclass
+import jakarta.persistence.PrePersist
 import org.springframework.data.annotation.CreatedDate
 import org.springframework.data.annotation.LastModifiedDate
 import java.time.Instant
@@ -14,5 +15,14 @@ abstract class AbstractTime(
 
     @LastModifiedDate
     @Column(name = "modified_at")
-    val modifiedAt: Instant = createdAt,
-)
+    var modifiedAt: Instant? = null,
+) {
+
+    @PrePersist
+    fun prePersist() {
+        modifiedAt = when (modifiedAt == null) {
+            true -> createdAt
+            false -> return
+        }
+    }
+}