diff --git a/frontend/src/components/PostEditForm.tsx b/frontend/src/components/PostEditForm.tsx
index 99039d9..f598bec 100644
--- a/frontend/src/components/PostEditForm.tsx
+++ b/frontend/src/components/PostEditForm.tsx
@@ -153,6 +153,21 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
     setDisabled (true)
     try
     {
+      const titleMissing = !title?.trim ()
+      const thumbnailMissing =
+	  !titleMissing
+	  && !(post.thumbnail?.trim () || post.thumbnailBase?.trim ())
+
+      if ((titleMissing || thumbnailMissing)
+	  && !(await dialogue.confirm ({
+	      title: titleMissing
+		  ? label ('edit.titleMissingConfirmation')
+		  : label ('edit.thumbnailMissingConfirmation'),
+	      confirmText: label ('shared:actions.update'),
+	      cancelText: label ('shared:actions.cancel'),
+	      closeLabel: label ('settings:actions.close') })))
+	return
+
       await update ({ id: post.id, title, tags, parentPostIds,
 		      duration: videoFlg ? duration : null,
 		      originalCreatedFrom, originalCreatedBefore },
diff --git a/frontend/src/locales/ain-Kana/posts.json b/frontend/src/locales/ain-Kana/posts.json
index 0310a6b..6ad0578 100644
--- a/frontend/src/locales/ain-Kana/posts.json
+++ b/frontend/src/locales/ain-Kana/posts.json
@@ -1,4 +1,5 @@
 {
+  "_untranslated": ["edit.titleMissingConfirmation", "edit.thumbnailMissingConfirmation"],
   "list": {
     "tagline": "{{brand}}",
     "empty": "ミンタㇻ　タ　ネン　カ　イサㇺ",
@@ -31,6 +32,8 @@
     "showExternal": "ソイタㇰ　ソㇱ　アヌカレ"
   },
   "edit": {
+    "titleMissingConfirmation": "タイトルが設定されてゐません．更新しますか?",
+    "thumbnailMissingConfirmation": "サムネールが設定されてゐません．更新しますか?",
     "validationFailed": "アシㇼ　カㇻ　カ　エアイカㇷ゚……",
     "conflictTitle": "モㇱマ　クㇽ　アシㇼ　カㇻ　ワ　アン！",
     "conflictDescription": "モㇱマ　イカㇻ　クㇽ　エエトコ　アシㇼ　カㇻ　ワ　アン。",
diff --git a/frontend/src/locales/ja/posts.json b/frontend/src/locales/ja/posts.json
index b6c1308..196289b 100644
--- a/frontend/src/locales/ja/posts.json
+++ b/frontend/src/locales/ja/posts.json
@@ -22,6 +22,8 @@
     "question": "表示しますか?", "showExternal": "外部ページを表示"
   },
   "edit": {
+    "titleMissingConfirmation": "タイトルが設定されてゐません．更新しますか?",
+    "thumbnailMissingConfirmation": "サムネールが設定されてゐません．更新しますか?",
     "validationFailed": "更新はできなかったよ……",
     "conflictTitle": "競合が発生しました．",
     "conflictDescription": "ほかの耕作員が先に更新してゐます．",