diff --git a/packages/frontend/src/components/MkPostForm.vue b/packages/frontend/src/components/MkPostForm.vue
index 0b5794d1e3..c16ef33414 100644
--- a/packages/frontend/src/components/MkPostForm.vue
+++ b/packages/frontend/src/components/MkPostForm.vue
@@ -251,6 +251,7 @@ const canPost = computed((): boolean => {
 			quoteId.value != null
 		) &&
 		(textLength.value <= maxTextLength.value) &&
+		(files.value.length > 16) &&
 		(!poll.value || poll.value.choices.length >= 2);
 });
 
diff --git a/packages/frontend/src/components/MkPostFormAttaches.vue b/packages/frontend/src/components/MkPostFormAttaches.vue
index 56e026aa3c..1336b61356 100644
--- a/packages/frontend/src/components/MkPostFormAttaches.vue
+++ b/packages/frontend/src/components/MkPostFormAttaches.vue
@@ -22,7 +22,9 @@ SPDX-License-Identifier: AGPL-3.0-only
 			</div>
 		</template>
 	</Sortable>
-	<p :class="$style.remain">{{ 16 - props.modelValue.length }}/16</p>
+	<p :class="[$style.remain, {
+		[$style.exceeded]: props.modelValue.length > 16,
+	}]">{{ 16 - props.modelValue.length }}/16</p>
 </div>
 </template>
 
@@ -239,5 +241,9 @@ function showFileMenu(file: Misskey.entities.DriveFile, ev: MouseEvent | Keyboar
 	margin: 0;
 	padding: 0;
 	font-size: 90%;
+
+	&.exceeded {
+		color: var(--MI_THEME-error);
+	}
 }
 </style>