diff --git a/crates/ruma-events/src/lib.rs b/crates/ruma-events/src/lib.rs
index c00737ae..097ab965 100644
--- a/crates/ruma-events/src/lib.rs
+++ b/crates/ruma-events/src/lib.rs
@@ -407,12 +407,11 @@ where
 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct PrivOwnedStr(Box<str>);
 
-/// Helper function for erroring when trying to serialize an event enum _Custom
-/// variant that can only be created by deserializing from an unknown event
-/// type.
+/// Helper function for erroring when trying to serialize an event enum _Custom variant that can
+/// only be created by deserializing from an unknown event type.
 #[doc(hidden)]
 #[allow(clippy::ptr_arg)]
-fn serialize_custom_event_error<S: Serializer>(_: &String, _: S) -> Result<S::Ok, S::Error> {
+pub fn serialize_custom_event_error<S: Serializer>(_: &String, _: S) -> Result<S::Ok, S::Error> {
     Err(serde::ser::Error::custom(
         "Failed to serialize event [content] enum: Unknown event type.\n\
          To send custom events, turn them into `Raw<EnumType>` by going through