diff --git a/changelog.d/13726.doc b/changelog.d/13726.doc
new file mode 100644
index 000000000000..ab840e1a92ae
--- /dev/null
+++ b/changelog.d/13726.doc
@@ -0,0 +1 @@
+Fix a mistake in the config manual: the `event_cache_size` _is_ scaled by `caches.global_factor`. The documentation was incorrect since Synapse 1.22.
diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
index 757957a1d58f..ae490d13a4ac 100644
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -1069,8 +1069,10 @@ Options related to caching.
 ---
 ### `event_cache_size`
 
-The number of events to cache in memory. Not affected by
-`caches.global_factor` and is not part of the `caches` section. Defaults to 10K.
+The number of events to cache in memory. Defaults to 10K. Like other caches,
+this is affected by `caches.global_factor` (see below).
+
+Note that this option is not part of the `caches` section.
 
 Example configuration:
 ```yaml