diff --git a/postgres-appliance/major_upgrade/inplace_upgrade.py b/postgres-appliance/major_upgrade/inplace_upgrade.py
index 2d4ade477..6fa9e31f5 100644
--- a/postgres-appliance/major_upgrade/inplace_upgrade.py
+++ b/postgres-appliance/major_upgrade/inplace_upgrade.py
@@ -529,10 +529,7 @@ def do_upgrade(self):
         if self.replica_connections:
             from patroni.postgresql.misc import parse_lsn
 
-            # Make sure we use the pg_controldata from the correct major version
-            self.postgresql.set_bin_dir(self.cluster_version)
             controldata = self.postgresql.controldata()
-            self.postgresql.set_bin_dir(self.desired_version)
 
             checkpoint_lsn = controldata.get('Latest checkpoint location')
             if controldata.get('Database cluster state') != 'shut down' or not checkpoint_lsn:
diff --git a/postgres-appliance/major_upgrade/pg_upgrade.py b/postgres-appliance/major_upgrade/pg_upgrade.py
index dee894b99..487fcd22d 100644
--- a/postgres-appliance/major_upgrade/pg_upgrade.py
+++ b/postgres-appliance/major_upgrade/pg_upgrade.py
@@ -35,7 +35,9 @@ def restore_shared_preload_libraries(self):
         return True
 
     def start_old_cluster(self, config, version):
-        self.set_bin_dir(version)
+        self._new_bin_dir = self._bin_dir
+        self.set_bin_dir_for_version(version)
+        self._old_bin_dir = self._bin_dir
 
         # make sure we don't archive wals from the old version
         self._old_config_values = {'archive_mode': self.config.get('parameters').get('archive_mode')}
@@ -50,11 +52,13 @@ def get_cluster_version(self):
         with open(self._version_file) as f:
             return f.read().strip()
 
-    def set_bin_dir(self, version):
+    def set_bin_dir_for_version(self, version):
         from spilo_commons import get_bin_dir
+        self.set_bin_dir(get_bin_dir(version))
 
-        self._old_bin_dir = self._bin_dir
-        self._bin_dir = get_bin_dir(version)
+    def set_bin_dir(self, bin_dir):
+        self._bin_dir = bin_dir
+        self._available_gucs = None
 
     @property
     def local_conn_kwargs(self):
@@ -168,7 +172,7 @@ def pg_upgrade(self, check=False):
         os.chdir(upgrade_dir)
 
         pg_upgrade_args = ['-k', '-j', str(psutil.cpu_count()),
-                           '-b', self._old_bin_dir, '-B', self._bin_dir,
+                           '-b', self._old_bin_dir, '-B', self._new_bin_dir,
                            '-d', self._data_dir, '-D', self._new_data_dir,
                            '-O', "-c timescaledb.restoring='on'",
                            '-O', "-c archive_mode='off'"]
@@ -180,8 +184,12 @@ def pg_upgrade(self, check=False):
         else:
             self.config.write_postgresql_conf()
 
+        self.set_bin_dir(self._new_bin_dir)
+
         logger.info('Executing pg_upgrade%s', (' --check' if check else ''))
         if subprocess.call([self.pgcommand('pg_upgrade')] + pg_upgrade_args) == 0:
+            if check:
+                self.set_bin_dir(self._old_bin_dir)
             os.chdir(old_cwd)
             shutil.rmtree(upgrade_dir)
             return True
@@ -206,7 +214,9 @@ def prepare_new_pgdata(self, version):
         old_version_file = self._version_file
         self._version_file = os.path.join(self._data_dir, 'PG_VERSION')
 
-        self.set_bin_dir(version)
+        self._old_bin_dir = self._bin_dir
+        self.set_bin_dir_for_version(version)
+        self._new_bin_dir = self._bin_dir
 
         # shared_preload_libraries for the old cluster, cleaned from incompatible/missing libs
         old_shared_preload_libraries = self.config.get('parameters').get('shared_preload_libraries')
@@ -239,6 +249,7 @@ def prepare_new_pgdata(self, version):
         self._new_data_dir, self._data_dir = self._data_dir, self._new_data_dir
         self.config._postgresql_conf = old_postgresql_conf
         self._version_file = old_version_file
+        self.set_bin_dir(self._old_bin_dir)
 
         if old_shared_preload_libraries:
             self.config.get('parameters')['shared_preload_libraries'] = old_shared_preload_libraries
diff --git a/postgres-appliance/tests/docker-compose.yml b/postgres-appliance/tests/docker-compose.yml
index a2b86e016..90a89f9f9 100644
--- a/postgres-appliance/tests/docker-compose.yml
+++ b/postgres-appliance/tests/docker-compose.yml
@@ -45,7 +45,9 @@ services:
                   loop_wait: 2
                   postgresql:
                     parameters:
+                      wal_decode_buffer_size: '521kB'
                       wal_keep_segments: 8
+                      jit: 'off'
               postgresql:
                 parameters:
                   shared_buffers: 32MB