diff --git a/changelog.d/5239.bugfix b/changelog.d/5239.bugfix
new file mode 100644
index 0000000000..dbb07be9e9
--- /dev/null
+++ b/changelog.d/5239.bugfix
@@ -0,0 +1 @@
+Fix 500 Internal Server Error when sending an event with `m.relates_to: null`.