diff --git a/metadata.py b/metadata.py
index 5c3b1e296..55f60296c 100644
--- a/metadata.py
+++ b/metadata.py
@@ -93,7 +93,8 @@ def meta_data_node_info(base_dir: str,
             "nodeName": domain,
             "mailerEnabled": False,
             "publicTimelineVisibility": {},
-            "postFormats": ["text/plain", "text/html", "text/markdown"],
+            "postFormats": ["text/plain", "text/html",
+                            "text/markdown", "text/x.misskeymarkdown"],
             "FEPs": ["c648", "521a", "8fcf", "4ccd", "c118", "fffd",
                      "1970", "0837", "7628", "2677", "5e53"]
         }
diff --git a/posts.py b/posts.py
index 0808eb89b..0afd978a1 100644
--- a/posts.py
+++ b/posts.py
@@ -139,7 +139,8 @@ def convert_post_content_to_html(message_json: {}) -> None:
         return
     if not obj_json.get('content'):
         return
-    if obj_json['mediaType'] != 'text/markdown':
+    if obj_json['mediaType'] not in ('text/markdown',
+                                     'text/x.misskeymarkdown'):
         return
     content_str = obj_json['content']
     obj_json['content'] = markdown_to_html(content_str)