diff --git a/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiSdt.c b/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiSdt.c
index 5aad7cca81..6146a1a309 100644
--- a/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiSdt.c
+++ b/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiSdt.c
@@ -562,6 +562,8 @@ Open (
   EFI_STATUS          Status;
   UINTN               MaxSize;
 
+  MaxSize = 0;
+
   //
   // Check for invalid input parameters
   //