diff --git a/packages/fcl-base/src/basenenc.pp b/packages/fcl-base/src/basenenc.pp
index d3e17f4e2a..73a4777cdf 100644
--- a/packages/fcl-base/src/basenenc.pp
+++ b/packages/fcl-base/src/basenenc.pp
@@ -97,7 +97,7 @@ Function Base64 : TAlphabetEncoder;
 Function Base64URL : TAlphabetEncoder;
 Function GetStandardEncoder(aEncoder : TStandardEncoder): TAlphabetEncoder;
 
-Function GetRawStringBytes(S : String) : TBytes;
+Function GetRawStringBytes(const S : String) : TBytes;
 Function GetRawStringFromBytes(B : TBytes) : RawByteString;
 
 implementation
@@ -114,7 +114,7 @@ begin
     Move(B[0],Result[1],L);
 end;
 
-Function GetRawStringBytes(S : String) : TBytes;
+Function GetRawStringBytes(Const S : String) : TBytes;
 
 Var
   L : Integer;