diff --git a/src/guide/xml/ch04.xml b/src/guide/xml/ch04.xml
index a2f366173..7069717fd 100644
--- a/src/guide/xml/ch04.xml
+++ b/src/guide/xml/ch04.xml
@@ -369,7 +369,7 @@ be made absolute against the base URI if the input document.
then URIs in the output are treated as parallel to the URIs in the input. If the
reference ../image.png works in the source document, it’s assumed
that will also work in the output document.
-If the mediaobject-input-base-uri is not empty, it is
+If the mediaobject-output-base-uri is not empty, it is
the base URI used for media objects. If this is a relative URI, it is taken to be
relative to the root of the output hierarchy.
Suppose the output base URI is https://images.example.com/, then