diff --git a/lib/MHA/HealthCheck.pm b/lib/MHA/HealthCheck.pm
index 8f2099e..d888517 100644
--- a/lib/MHA/HealthCheck.pm
+++ b/lib/MHA/HealthCheck.pm
@@ -119,7 +119,7 @@ sub connect {
             "MySQL Ping($self->{ping_type})" );
         };
         if ($@) {
-          my $msg = "Unexpected error heppened when pinging! $@";
+          my $msg = "Unexpected error happened when pinging! $@";
           $log->error($msg);
           undef $@;
           $child_exit_code = 1;
diff --git a/lib/MHA/MasterMonitor.pm b/lib/MHA/MasterMonitor.pm
index 2a6ac56..e608094 100644
--- a/lib/MHA/MasterMonitor.pm
+++ b/lib/MHA/MasterMonitor.pm
@@ -166,11 +166,11 @@ sub check_binlog($) {
 }
 
 sub check_slave_env() {
-  my @alive_servers = $_server_manager->get_alive_slaves();
+  my @alive_slaves = $_server_manager->get_alive_slaves();
   $log->info(
 "Checking SSH publickey authentication and checking recovery script configurations on all alive slave servers.."
   );
-  foreach my $s (@alive_servers) {
+  foreach my $s (@alive_slaves) {
     my $ssh_user_host = $s->{ssh_user} . '@' . $s->{ssh_ip};
     my $command =
 "apply_diff_relay_logs --command=test --slave_user=$s->{escaped_user} --slave_host=$s->{hostname} --slave_ip=$s->{ip} --slave_port=$s->{port} --workdir=$s->{remote_workdir} --target_version=$s->{mysql_version} --manager_version=$MHA::ManagerConst::VERSION";
diff --git a/lib/MHA/MasterRotate.pm b/lib/MHA/MasterRotate.pm
index cf630f4..0347ca2 100644
--- a/lib/MHA/MasterRotate.pm
+++ b/lib/MHA/MasterRotate.pm
@@ -621,6 +621,11 @@ sub do_master_online_switch {
   eval {
     $orig_master = identify_orig_master();
     my $new_master = identify_new_master($orig_master);
+    
+    if ($orig_master->{id} == $new_master->{id}){
+      croak "new_master is equal as orig_master, no need to switch master!\n";
+    }
+    
     $log->info("** Phase 1: Configuration Check Phase completed.\n");
     $log->info();