diff --git a/MdePkg/Library/BaseLib/String.c b/MdePkg/Library/BaseLib/String.c
index 6198ccbc96..45198373f2 100644
--- a/MdePkg/Library/BaseLib/String.c
+++ b/MdePkg/Library/BaseLib/String.c
@@ -1978,6 +1978,9 @@ Base64Decode (
   UINT32  Accumulator;
   UINTN   OriginalDestinationSize;
   UINTN   SourceIndex;
+  CHAR8   SourceChar;
+  UINT32  Base64Value;
+  UINT8   DestinationOctet;
 
   if (DestinationSize == NULL) {
     return RETURN_INVALID_PARAMETER;
@@ -2054,10 +2057,6 @@ Base64Decode (
   // Decoding loop.
   //
   for (SourceIndex = 0; SourceIndex < SourceSize; SourceIndex++) {
-    CHAR8  SourceChar;
-    UINT32 Base64Value;
-    UINT8  DestinationOctet;
-
     SourceChar = Source[SourceIndex];
 
     //