diff --git a/changelog.d/3456.bugfix b/changelog.d/3456.bugfix
new file mode 100644
index 000000000..66e67036c
--- /dev/null
+++ b/changelog.d/3456.bugfix
@@ -0,0 +1,2 @@
+Synapse is now stricter regarding accepting events which it cannot 
+retrieve the prev_events for.