diff --git a/docs/en/reference/annotations-reference.rst b/docs/en/reference/annotations-reference.rst
index 03a6d4454..5979939ea 100644
--- a/docs/en/reference/annotations-reference.rst
+++ b/docs/en/reference/annotations-reference.rst
@@ -236,11 +236,14 @@ Example:
 @DiscriminatorColumn
 ~~~~~~~~~~~~~~~~~~~~~
 
-This annotation is a required annotation for the topmost/super
+This annotation is an optional annotation for the topmost/super
 class of an inheritance hierarchy. It specifies the details of the
 column which saves the name of the class, which the entity is
 actually instantiated as.
 
+If this annotation is not specified, the discriminator column defaults
+to a string column of length 255 called ``dtype``.
+
 Required attributes: