diff --git a/src/fanbox/item.rs b/src/fanbox/item.rs
index 636c2f8..44befab 100644
--- a/src/fanbox/item.rs
+++ b/src/fanbox/item.rs
@@ -1,5 +1,8 @@
+use super::check::CheckUnknown;
+use super::error::FanboxAPIError;
 use crate::parser::json::parse_u64;
 use json::JsonValue;
+use proc_macros::check_json_keys;
 use std::fmt::Debug;
 
 /// To represent a fanbox item
@@ -144,6 +147,37 @@ impl FanboxItem {
     }
 }
 
+impl CheckUnknown for FanboxItem {
+    fn check_unknown(&self) -> Result<(), FanboxAPIError> {
+        check_json_keys!(
+            "id"+,
+            "commentCount"+,
+            "coverImageUrl",
+            "cover": [
+                "type"+,
+                "url",
+            ],
+            "creatorId"+,
+            "excerpt"+,
+            "feeRequired"+,
+            "hasAdultContent"+,
+            "isLiked"+,
+            "isRestricted"+,
+            "likeCount"+,
+            "publishedDatetime"+,
+            "tags"+,
+            "title"+,
+            "updatedDatetime"+,
+            "user": [
+                "name"+author_name,
+                "iconUrl",
+                "id"+,
+            ],
+        );
+        Ok(())
+    }
+}
+
 impl Debug for FanboxItem {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("FanboxItem")
diff --git a/src/fanbox/item_list.rs b/src/fanbox/item_list.rs
index fa67de1..51533cd 100644
--- a/src/fanbox/item_list.rs
+++ b/src/fanbox/item_list.rs
@@ -1,3 +1,4 @@
+use super::check::CheckUnknown;
 use super::error::FanboxAPIError;
 use super::item::FanboxItem;
 use crate::fanbox_api::FanboxClientInternal;
@@ -24,18 +25,20 @@ impl FanboxItemList {
     pub async fn get_next_page(&self) -> Result<FanboxItemList, FanboxAPIError> {
         match &self.next_url {
             Some(url) => {
-                match self.client.get_url(url, gettext("Failed to get next page of the items."), gettext("Items data:")).await {
-                    Some(data) => {
-                        Self::new(&data["body"], Arc::clone(&self.client))
-                    }
-                    None => {
-                        Err(FanboxAPIError::from("Failed to get next page."))
-                    }
+                match self
+                    .client
+                    .get_url(
+                        url,
+                        gettext("Failed to get next page of the items."),
+                        gettext("Items data:"),
+                    )
+                    .await
+                {
+                    Some(data) => Self::new(&data["body"], Arc::clone(&self.client)),
+                    None => Err(FanboxAPIError::from("Failed to get next page.")),
                 }
             }
-            None => {
-                Err(FanboxAPIError::from("No next url, can not get next page."))
-            }
+            None => Err(FanboxAPIError::from("No next url, can not get next page.")),
         }
     }
 
@@ -70,6 +73,15 @@ impl FanboxItemList {
     }
 }
 
+impl CheckUnknown for FanboxItemList {
+    fn check_unknown(&self) -> Result<(), FanboxAPIError> {
+        for i in self.items.iter() {
+            i.check_unknown()?;
+        }
+        Ok(())
+    }
+}
+
 impl Debug for FanboxItemList {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("FanboxItemList")