diff --git a/src/components/post_status_form/post_status_form.js b/src/components/post_status_form/post_status_form.js
index 72fd29aa..6eee23ce 100644
--- a/src/components/post_status_form/post_status_form.js
+++ b/src/components/post_status_form/post_status_form.js
@@ -154,7 +154,7 @@ const PostStatusForm = {
     }
 
     const { postContentType: contentType, postLanguage: defaultPostLanguage, sensitiveByDefault, sensitiveIfSubject, interfaceLanguage, alwaysShowSubjectInput } = this.$store.getters.mergedConfig
-    const postLanguage = defaultPostLanguage || interfaceLanguage
+    const postLanguage = defaultPostLanguage || interfaceToISOLanguage(interfaceLanguage)
 
     let statusParams = {
       spoilerText: this.subject || '',