diff --git a/test/lib/pgBackRestTest/Env/Host/HostDbTest.pm b/test/lib/pgBackRestTest/Env/Host/HostDbTest.pm
index 4b2a98329..34598a778 100644
--- a/test/lib/pgBackRestTest/Env/Host/HostDbTest.pm
+++ b/test/lib/pgBackRestTest/Env/Host/HostDbTest.pm
@@ -466,11 +466,17 @@ sub clusterStop
     # Disconnect user session
     $self->sqlDisconnect();
 
-    # Grep for errors in postgresql.log - this is done first because we want to ignore any errors that happen during shutdown
+    # Grep for errors in postgresql.log - this is done first because we want to ignore any errors that happen during shutdown.
+    #
+    # The unsupported version error is showing up on older versions of PostgreSQL (e.g. 9.1, 9.2) on RHEL6 when setting up a standby
+    # with streaming replication. The error occurs when a client does not properly send a version number and it's not clear why it
+    # is happening here, but it does not appear to have anything to do with pgBackRest and only affects RHEL6, i.e. 9.1 and 9.2
+    # do not show this error on other distros. For now ignore the error since RHEL6 is nearly EOL.
     if (!$bIgnoreLogError && storageTest()->exists($self->pgLogFile()))
     {
         $self->executeSimple(
-            'grep -v "FATAL\:  57P03\: the database system is starting up" ' . $self->pgLogFile() . ' | grep "ERROR\|FATAL"',
+            'grep -v "\(FATAL\:  57P03\: the database system is starting up"\)\|\(FATAL\:  0A000\: unsupported frontend protocol\)" ' .
+                $self->pgLogFile() . ' | grep "ERROR\|FATAL"',
             {iExpectedExitStatus => 1});
     }