diff --git a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c
index fc40112b54..42b73f60ea 100644
--- a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c
+++ b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c
@@ -381,7 +381,7 @@ UpdateMailboxContent (
     Mailbox->HostSequenceNo = (UINT8) Value;
     break;
   case DEBUG_MAILBOX_DEBUG_TIMER_FREQUENCY:
-    Mailbox->ToBeCheckSum = Mailbox->CheckSum + CalculateSum8 ((UINT8 *)&Mailbox->HostSequenceNo, sizeof(UINT32))
+    Mailbox->ToBeCheckSum = Mailbox->CheckSum + CalculateSum8 ((UINT8 *)&Mailbox->DebugTimerFrequency, sizeof(UINT32))
                                               - CalculateSum8 ((UINT8 *)&Value, sizeof(UINT32));
     Mailbox->DebugTimerFrequency = (UINT32) Value;
     break;
diff --git a/SourceLevelDebugPkg/Library/DebugAgent/SecPeiDebugAgent/SecPeiDebugAgentLib.c b/SourceLevelDebugPkg/Library/DebugAgent/SecPeiDebugAgent/SecPeiDebugAgentLib.c
index b718e82e20..ec389c7e8b 100644
--- a/SourceLevelDebugPkg/Library/DebugAgent/SecPeiDebugAgent/SecPeiDebugAgentLib.c
+++ b/SourceLevelDebugPkg/Library/DebugAgent/SecPeiDebugAgent/SecPeiDebugAgentLib.c
@@ -522,6 +522,10 @@ InitializeDebugAgent (
     // Build mailbox in HOB and setup Mailbox Set In Pei flag
     //
     Mailbox = AllocateZeroPool (sizeof (DEBUG_AGENT_MAILBOX));
+    if (Mailbox == NULL) {
+      DEBUG ((EFI_D_ERROR, "DebugAgent: Failed to allocate memory!\n"));
+      CpuDeadLoop ();
+    }
     MailboxLocation = (UINT64)(UINTN)Mailbox;
     MailboxLocationPointer = BuildGuidDataHob (
                                &gEfiDebugAgentGuid,