diff --git a/helpers/postgresql.py b/helpers/postgresql.py
index d8653e96..dd8ad4c6 100644
--- a/helpers/postgresql.py
+++ b/helpers/postgresql.py
@@ -146,7 +146,7 @@ class Postgresql:
                 member_conn.autocommit = True
                 member_cursor = member_conn.cursor()
                 member_cursor.execute(
-                    'SELECT %s::pg_lsn - pg_last_xlog_replay_location() AS bytes', (self.xlog_position(), ))
+                    "SELECT %s - (pg_last_xlog_replay_location() - '0/0000000'::pg_lsn)", (self.xlog_position(), ))
                 xlog_diff = member_cursor.fetchone()[0]
                 logger.info([self.name, member['hostname'], xlog_diff])
                 if xlog_diff < 0:
@@ -216,7 +216,7 @@ primary_conninfo = '{}'
             self.replication['username']), self.replication['password'])
 
     def xlog_position(self):
-        return self.query('SELECT pg_last_xlog_replay_location()').fetchone()[0]
+        return self.query("SELECT pg_last_xlog_replay_location() - '0/0000000'::pg_lsn").fetchone()[0]
 
     def load_replication_slots(self):
         cursor = self.query("SELECT slot_name FROM pg_replication_slots WHERE slot_type='physical'")