diff --git a/setup.cfg b/setup.cfg
index e9b7db71..54819a95 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -4,7 +4,7 @@ author= Tskit Developers
 author_email = admin@tskit.dev
 license = GNU GPLv3+
 description= Infer tree sequences from genetic variation data.
-long_description_content_type = text/x-markdown
+long_description_content_type = text/markdown
 long_description = file: README.md
 url = https://tskit.dev/tsinfer
 project_urls =