diff --git a/app/src/main/java/jp/juggler/subwaytooter/util/PostImpl.kt b/app/src/main/java/jp/juggler/subwaytooter/util/PostImpl.kt
index 43dc016c..6ca853c7 100644
--- a/app/src/main/java/jp/juggler/subwaytooter/util/PostImpl.kt
+++ b/app/src/main/java/jp/juggler/subwaytooter/util/PostImpl.kt
@@ -607,7 +607,19 @@ class PostImpl(
                         status != null ->
                             PostResult.Normal(account, status)
 
-                        else -> error(result.error ?: "(result.error is null)")
+                        else -> {
+                            val e = result.error
+                            error(
+                                when {
+                                    e.isNullOrBlank() -> "(missing result.error)"
+
+                                    e.contains("HTTP 404") ->
+                                        "$e\n${activity.getString(R.string.post_404_desc)}"
+
+                                    else -> e
+                                }
+                            )
+                        }
                     }
                 }
             }
diff --git a/app/src/main/res/values-ja/strings.xml b/app/src/main/res/values-ja/strings.xml
index e8d2b42a..dac02264 100644
--- a/app/src/main/res/values-ja/strings.xml
+++ b/app/src/main/res/values-ja/strings.xml
@@ -1289,4 +1289,5 @@
     <string name="use_webp_format_if_server_accepts">可能ならWebPフォーマットを使う</string>
     <string name="detail">詳細</string>
     <string name="emoji_detail">絵文字の詳細</string>
-</resources>
\ No newline at end of file
+    <string name="post_404_desc">(もしくは、フォロー限定投稿にフォロー外から返信しようとしました)</string>
+</resources>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 500c54ee..75a727d9 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -1300,4 +1300,5 @@
     <string name="use_webp_format_if_server_accepts">Use WebP format if server accepts.</string>
     <string name="detail">Detail</string>
     <string name="emoji_detail">Emoji detail</string>
+    <string name="post_404_desc">(Or, you reply to follower-only post from other account)</string>
 </resources>
diff --git a/base/src/main/java/jp/juggler/util/log/ToastUtils.kt b/base/src/main/java/jp/juggler/util/log/ToastUtils.kt
index 04b4f742..8fc534de 100644
--- a/base/src/main/java/jp/juggler/util/log/ToastUtils.kt
+++ b/base/src/main/java/jp/juggler/util/log/ToastUtils.kt
@@ -108,7 +108,7 @@ internal fun showToastImpl(
     context: Context,
     bLong: Boolean,
     message: String,
-    forceToast:Boolean = false,
+    forceToast: Boolean = false,
 ): Boolean {
     runOnMainLooper {
         if (!forceToast && (message.length >= 32 || message.count { it == '\n' } > 1)) {
@@ -154,8 +154,8 @@ internal fun showToastImpl(
 fun Context.showToast(
     bLong: Boolean,
     caption: String?,
-    forceToast:Boolean = false,
-): Boolean = showToastImpl(this, bLong, caption ?: "(null)" ,forceToast = forceToast)
+    forceToast: Boolean = false,
+): Boolean = showToastImpl(this, bLong, caption ?: "(null)", forceToast = forceToast)
 
 fun Context.showToast(ex: Throwable, caption: String? = null): Boolean =
     showToastImpl(this, true, ex.withCaption(caption))
@@ -188,23 +188,26 @@ fun AppCompatActivity.showError(ex: Throwable, caption: String? = null) {
     if (ex is CancellationException) return
 
     try {
-        AlertDialog.Builder(this)
-            .setTitle("error")
-            .setMessage(
-                listOf(
-                    caption,
-                    when (ex) {
-                        is IllegalStateException -> null
-                        else -> ex.javaClass.simpleName
-                    },
-                    ex.message,
-                )
-                    .filter { !it.isNullOrBlank() }
-                    .joinToString("\n")
-            )
+        val text = listOf(
+            caption,
+            when (ex) {
+                is IllegalStateException -> null
+                else -> ex.javaClass.simpleName
+            },
+            ex.message,
+        )
+            .filter { !it.isNullOrBlank() }
+            .joinToString("\n")
+        if (text.isNotEmpty()) {
+            AlertDialog.Builder(this)
+                .setMessage(text)
+                .setPositiveButton(android.R.string.ok, null)
+                .show()
+            return
+        }
     } catch (ignored: Throwable) {
-        showToast(ex, caption)
     }
+    showToast(ex, caption)
 }
 
 fun Context.errorString(@StringRes stringId: Int, vararg args: Any?): Nothing =