diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 93fe5b116df..e8d064ecd8d 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -94,6 +94,17 @@ log_statement=all
 log_error_verbosity=default
 restart_after_crash=false
 temp_buffers=100
+));
+
+	# Even though we used -c io_method=... above, if TEMP_CONFIG sets
+	# io_method, it'd override the setting persisted at initdb time. While
+	# using (and later verifying) the setting from initdb provides some
+	# verification of having used the io_method during initdb, it's probably
+	# not worth the complication of only appending if the variable is set in
+	# in TEMP_CONFIG.
+	$node->append_conf(
+		'postgresql.conf', qq(
+io_method=$io_method
 ));
 
 	ok(1, "$io_method: initdb");