diff --git a/jsonschema-validation.xml b/jsonschema-validation.xml
index 20a6b799..06966a8d 100644
--- a/jsonschema-validation.xml
+++ b/jsonschema-validation.xml
@@ -1023,7 +1023,8 @@
                     JSON Schema's data model.
                 </t>
                 <t>
-                    The value of this property SHOULD be ignored if "contentMediaType" is not present.
+                    The value of this property MUST be a valid JSON schema. It SHOULD be ignored if
+                    "contentMediaType" is not present.
                 </t>
             </section>