diff --git a/packages/client/src/components/MkMedia.vue b/packages/client/src/components/MkMedia.vue
index 4c023f1310..2cbb881f35 100644
--- a/packages/client/src/components/MkMedia.vue
+++ b/packages/client/src/components/MkMedia.vue
@@ -54,7 +54,7 @@
 					controls
 					@contextmenu.stop
 				>
-					<source :src="media.url" :type="media.type" />
+					<source :src="media.url" :type="mediaType" />
 				</video>
 			</VuePlyr>
 		</template>
@@ -80,7 +80,7 @@
 </template>
 
 <script lang="ts" setup>
-import { watch, ref } from "vue";
+import { watch, ref, computed } from "vue";
 import VuePlyr from "vue-plyr";
 import "vue-plyr/dist/vue-plyr.css";
 import type * as misskey from "calckey-js";
@@ -107,6 +107,10 @@ const url =
 		? getStaticImageUrl(props.media.thumbnailUrl)
 		: props.media.thumbnailUrl;
 
+const mediaType = computed(() => {
+	return props.media.type === 'video/quicktime' ? 'video/mp4' : props.media.type;
+});
+
 function captionPopup() {
 	os.alert({
 		type: "info",