diff --git a/MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.c b/MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.c
index e3b2846c09..e818543d92 100644
--- a/MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.c
+++ b/MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.c
@@ -40,14 +40,14 @@ FillBuf (
   //
   // Left shift NumOfBits of bits in advance
   //
-  Sd->mBitBuf = (UINT32) (Sd->mBitBuf << NumOfBits);
+  Sd->mBitBuf = (UINT32) LShiftU64 (((UINT64)Sd->mBitBuf), NumOfBits);
 
   //
   // Copy data needed in bytes into mSbuBitBuf
   //
   while (NumOfBits > Sd->mBitCount) {
-
-    Sd->mBitBuf |= (UINT32) (Sd->mSubBitBuf << (NumOfBits = (UINT16) (NumOfBits - Sd->mBitCount)));
+    NumOfBits = (UINT16) (NumOfBits - Sd->mBitCount);
+    Sd->mBitBuf |= (UINT32) LShiftU64 (((UINT64)Sd->mSubBitBuf), NumOfBits);
 
     if (Sd->mCompSize > 0) {
       //