diff --git a/mattermost.el b/mattermost.el
index b4e500b..926aadc 100644
--- a/mattermost.el
+++ b/mattermost.el
@@ -132,7 +132,7 @@ if the user is not present"
   "Builds a Mattermost request and returns the JSON response"
   (let ((url-request-method method)
         (url-request-extra-headers `(("Content-Type" . "application/json")))
-        (url-request-data (if body (json-serialize body))))
+        (url-request-data (if body (encode-coding-string (json-serialize body) 'utf-8))))
     (if mattermost-token
         (add-to-list 'url-request-extra-headers `("Authorization" . ,(concat "Bearer " mattermost-token))))
     (with-current-buffer (url-retrieve-synchronously (concat "https://" mattermost-host "/api/v4" url) t)