diff --git a/postgres-appliance/major_upgrade/pg_upgrade.py b/postgres-appliance/major_upgrade/pg_upgrade.py
index 72c68f0ad..487fcd22d 100644
--- a/postgres-appliance/major_upgrade/pg_upgrade.py
+++ b/postgres-appliance/major_upgrade/pg_upgrade.py
@@ -54,9 +54,7 @@ def get_cluster_version(self):
 
     def set_bin_dir_for_version(self, version):
         from spilo_commons import get_bin_dir
-
-        self._bin_dir = get_bin_dir(version)
-        self._available_gucs = None
+        self.set_bin_dir(get_bin_dir(version))
 
     def set_bin_dir(self, bin_dir):
         self._bin_dir = bin_dir
diff --git a/postgres-appliance/tests/docker-compose.yml b/postgres-appliance/tests/docker-compose.yml
index 48b5ef277..90a89f9f9 100644
--- a/postgres-appliance/tests/docker-compose.yml
+++ b/postgres-appliance/tests/docker-compose.yml
@@ -45,6 +45,7 @@ services:
                   loop_wait: 2
                   postgresql:
                     parameters:
+                      wal_decode_buffer_size: '521kB'
                       wal_keep_segments: 8
                       jit: 'off'
               postgresql: