diff --git a/src/rcore/modes.rs b/src/rcore/modes.rs
index 03b8fbc..b8140a9 100644
--- a/src/rcore/modes.rs
+++ b/src/rcore/modes.rs
@@ -59,6 +59,11 @@ pub trait Mode {
     /// Discard any extra information contained in [`Mode::ParseSuccess`].
     fn seal<A, I>(s: Self::ParseSuccess<A, I>) -> A;
 
+    /// Map the error of an extension result.
+    ///
+    /// Useful for for wrappers and chaining parsing after [`InliningFactory`].
+    ///
+    /// [`InliningFactory`]: crate::rstd::inlining::InliningFactory
     fn xmap_err<A, E0, E1>(
         result: Self::ExtensionResult<A, E0>,
         f: impl FnOnce(E0) -> E1,