diff --git a/doc/gf-refman.html b/doc/gf-refman.html
index 376689a9a..d82fa9488 100644
--- a/doc/gf-refman.html
+++ b/doc/gf-refman.html
@@ -5,7 +5,7 @@
GF Language Reference Manual
-Aarne Ranta, Krasimir Angelov
November 2013
+Aarne Ranta, Krasimir Angelov
June 2014, GF 3.6
@@ -2490,8 +2490,20 @@ The result is a record type or a record with a union of the fields of R a
- both R and S are either records or record types
-
- the labels in R and S are distinct
+
- the labels in R and S are disjoint, if R and S are record types
+(Since GF version 3.6) If R and S are record objects,
+then the labels in them need not be disjoint. Labels defined in
+S are then given priority, so that record extensions in fact
+works as record update. A common pattern of using this feature
+is
+
+ lin F x ... = x ** {r = ... x.r ...}
+
+where x is a record with many fields, just one of which is
+updated. Following the normal binding conditions, x.r on the
+right hand side still refers to the old value of the r field.
+
Subtyping