diff --git a/README.md b/README.md
index e303d494..62ca5323 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,16 @@
-
-
-
+# Flatpak 1.4.x: end-of-life branch
+
+The Flatpak 1.4.x branch is no longer supported and does not receive
+security fixes.
+Please upgrade to a supported branch as documented in
+[SECURITY.md](https://github.com/flatpak/flatpak/blob/main/SECURITY.md).
+
+If maintainers of long-term-supported OS distributions are still
+distributing Flatpak 1.4.x, those vendors will need to either take
+responsibility for backporting security fixes, or upgrade their Flatpak
+packages.
+
+---
[](https://lgtm.com/projects/g/flatpak/flatpak/context:python)