diff --git a/EdkCompatibilityPkg/Foundation/Library/EdkIIGlueLib/Library/BaseMemoryLib/X64/CopyMem.asm b/EdkCompatibilityPkg/Foundation/Library/EdkIIGlueLib/Library/BaseMemoryLib/X64/CopyMem.asm
index a2e04056fd..c2b5d6f92f 100644
--- a/EdkCompatibilityPkg/Foundation/Library/EdkIIGlueLib/Library/BaseMemoryLib/X64/CopyMem.asm
+++ b/EdkCompatibilityPkg/Foundation/Library/EdkIIGlueLib/Library/BaseMemoryLib/X64/CopyMem.asm
@@ -39,7 +39,7 @@ InternalMemCopyMem  PROC    USES    rsi rdi
     cmp     rsi, rdi
     mov     rax, rdi                    ; rax <- Destination as return value
     jae     @F
-    cmp     r9, rsi
+    cmp     r9, rdi
     jae     @CopyBackward               ; Copy backward if overlapped
 @@:
     mov     rcx, r8