diff --git a/doc/man7/property.pod b/doc/man7/property.pod
index 3d6f269d7f..bc57a67648 100644
--- a/doc/man7/property.pod
+++ b/doc/man7/property.pod
@@ -158,6 +158,9 @@ The lexical syntax in EBNF is given by:
  NumberLiteral  ::= '0' ( [0-7]* | 'x' [0-9A-Fa-f]+ ) | '-'? [1-9] [0-9]+
  PropertyName   ::= [A-Za-z] [A-Za-z0-9_]* ( '.' [A-Za-z] [A-Za-z0-9_]* )*
 
+The flavour of EBNF being used is defined by:
+L<https://www.w3.org/TR/2010/REC-xquery-20101214/#EBNFNotation>.
+
 =head1 HISTORY
 
 Properties were added in OpenSSL 3.0