diff --git a/src/rcore.rs b/src/rcore.rs
index 71acf61..3477aca 100644
--- a/src/rcore.rs
+++ b/src/rcore.rs
@@ -33,9 +33,9 @@ pub use self::hashing::{Hash, HASH_SIZE, HASH_ZEROS};
 pub use self::inctx::InCtx;
 pub use self::inlining::{Inlining, InliningExt, InliningResultExt};
 pub use self::modes::{
-    ExtensionResult, ExtensionResultM, ExtensionSourceM, FactoryModeParse, FactoryModeProxy,
-    ImplMode, Mode, ModeResult, ParseMode, ParseModeExt, ParseResultM, QRegularFactory,
-    RegularFactory, RegularMode, WithMode, WithParseMode,
+    ExtensionResult, ExtensionResultM, ExtensionSource, ExtensionSourceM, FactoryModeParse,
+    FactoryModeProxy, ImplMode, Mode, ModeResult, ParseMode, ParseModeExt, ParseResultM,
+    QRegularFactory, RegularFactory, RegularMode, WithMode, WithParseMode,
 };
 pub use self::origin::{OFctr, Origin};
 pub use self::point::Point;
diff --git a/src/rcore/modes.rs b/src/rcore/modes.rs
index 34f3fb7..12198bf 100644
--- a/src/rcore/modes.rs
+++ b/src/rcore/modes.rs
@@ -6,7 +6,10 @@ use super::*;
 pub type ModeResult<M, A, E, I> = Result<<M as Mode>::ParseSuccess<A, I>, E>;
 
 /// [`Mode`] equivalent of [`ParseResult`] for extension.
-pub type ExtensionResult<M, A, E> = <M as Mode>::ParseSuccess<A, E>;
+pub type ExtensionResult<M, A, E> = <M as Mode>::ExtensionResult<A, E>;
+
+/// See [`Mode::prepare`].
+pub type ExtensionSource<M, A> = <M as Mode>::ExtensionSource<A>;
 
 /// Mode of parsing.
 ///