diff --git a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
index 9477b94044..b4cb48843f 100644
--- a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
+++ b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
@@ -225,6 +225,8 @@ FindGuardedMemoryMap (
   UINTN                   BitsToUnitEnd;
   EFI_STATUS              Status;
 
+  MapMemory = 0;
+
   //
   // Adjust current map table depth according to the address to access
   //