diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 6376f5f1e3e..fcf8e0db5ae 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -6595,6 +6595,9 @@ myEventProc(PGEventId evtId, void *evtInfo, void *passThrough)
       </indexterm>
       <envar>PGREQUIRESSL</envar> behaves the same as the <xref
       linkend="libpq-connect-requiressl"> connection parameter.
+      This environment variable is deprecated in favor of the
+      <envar>PGSSLMODE</envar> variable, but setting both variables suppresses
+      the effect of <envar>PGSSLMODE</envar>.
      </para>
     </listitem>