diff --git a/contrib/pg_prewarm/autoprewarm.c b/contrib/pg_prewarm/autoprewarm.c
index 9ea6c2252a..06ee21d496 100644
--- a/contrib/pg_prewarm/autoprewarm.c
+++ b/contrib/pg_prewarm/autoprewarm.c
@@ -164,8 +164,14 @@ autoprewarm_main(Datum main_arg)
 	if (apw_init_shmem())
 		first_time = false;
 
-	/* Set on-detach hook so that our PID will be cleared on exit. */
-	on_shmem_exit(apw_detach_shmem, 0);
+	/*
+	 * Set on-detach hook so that our PID will be cleared on exit.
+	 *
+	 * NB: Autoprewarm's state is stored in a DSM segment, and DSM segments
+	 * are detached before calling the on_shmem_exit callbacks, so we must put
+	 * apw_detach_shmem in the before_shmem_exit callback list.
+	 */
+	before_shmem_exit(apw_detach_shmem, 0);
 
 	/*
 	 * Store our PID in the shared memory area --- unless there's already
diff --git a/contrib/pg_prewarm/t/001_basic.pl b/contrib/pg_prewarm/t/001_basic.pl
index bcd23a6914..825d3448ee 100644
--- a/contrib/pg_prewarm/t/001_basic.pl
+++ b/contrib/pg_prewarm/t/001_basic.pl
@@ -55,4 +55,10 @@ $node->wait_for_log(
 
 $node->stop;
 
+# control file should indicate normal shut down
+command_like(
+	[ 'pg_controldata', $node->data_dir() ],
+	qr/Database cluster state:\s*shut down/,
+	'cluster shut down normally');
+
 done_testing();