diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index 42011d6231..742f0c1f5e 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -330,6 +330,7 @@ SortApicId (
   CPU_INFO_IN_HOB   CpuInfo;
   UINT32            ApCount;
   CPU_INFO_IN_HOB   *CpuInfoInHob;
+  volatile UINT32   *StartupApSignal;
 
   ApCount = CpuMpData->CpuCount - 1;
   CpuInfoInHob = (CPU_INFO_IN_HOB *) (UINTN) CpuMpData->CpuInfoInHob;
@@ -354,6 +355,14 @@ SortApicId (
           sizeof (CPU_INFO_IN_HOB)
           );
         CopyMem (&CpuInfoInHob[Index1], &CpuInfo, sizeof (CPU_INFO_IN_HOB));
+
+        //
+        // Also exchange the StartupApSignal.
+        //
+        StartupApSignal = CpuMpData->CpuData[Index3].StartupApSignal;
+        CpuMpData->CpuData[Index3].StartupApSignal =
+          CpuMpData->CpuData[Index1].StartupApSignal;
+        CpuMpData->CpuData[Index1].StartupApSignal = StartupApSignal;
       }
     }