diff --git a/doc/src/sgml/pgtrgm.sgml b/doc/src/sgml/pgtrgm.sgml
index 7e292822553..fefe30afb7c 100644
--- a/doc/src/sgml/pgtrgm.sgml
+++ b/doc/src/sgml/pgtrgm.sgml
@@ -416,6 +416,8 @@
    the above-described similarity operators, and additionally support
    trigram-based index searches for <literal>LIKE</literal>, <literal>ILIKE</literal>,
    <literal>~</literal>, <literal>~*</literal> and <literal>=</literal> queries.
+   The similarity comparisons are case-insensitive in a default build of
+   <filename>pg_trgm</filename>.
    Inequality operators are not supported.
    Note that those indexes may not be as efficient as regular B-tree indexes
    for equality operator.