diff --git a/MdePkg/Library/BaseLib/X64/SwitchStack.c b/MdePkg/Library/BaseLib/X64/SwitchStack.c
index 3dd93825e0..64ae261263 100644
--- a/MdePkg/Library/BaseLib/X64/SwitchStack.c
+++ b/MdePkg/Library/BaseLib/X64/SwitchStack.c
@@ -14,6 +14,15 @@
 
 **/
 
+VOID
+EFIAPI
+_SwitchStack (
+  IN      SWITCH_STACK_ENTRY_POINT  EntryPoint,
+  IN      VOID                      *Context1,
+  IN      VOID                      *Context2,
+  IN      VOID                      *NewStack
+  );
+
 /**
   Transfers control to a function starting with a new stack.