diff --git a/doc/src/sgml/bgworker.sgml b/doc/src/sgml/bgworker.sgml
index 1151161..aeac19a 100644
--- a/doc/src/sgml/bgworker.sgml
+++ b/doc/src/sgml/bgworker.sgml
@@ -64,7 +64,10 @@ typedef struct BackgroundWorker
    <literal>BGWORKER_SHMEM_ACCESS</literal> (requesting shared memory access)
    and <literal>BGWORKER_BACKEND_DATABASE_CONNECTION</literal> (requesting the
    ability to establish a database connection, through which it can later run
-   transactions and queries).
+   transactions and queries). A background worker using <literal>
+   BGWORKER_BACKEND_DATABASE_CONNECTION</literal> to connect to a database
+   need also to attach shared memory with <literal>BGWORKER_SHMEM_ACCESS
+   </literal>, or worker start-up will fail.
   </para>
 
   <para>