diff --git a/lib/delphi/src/Thrift.Protocol.JSON.pas b/lib/delphi/src/Thrift.Protocol.JSON.pas
index dfab86b..3c54386 100644
--- a/lib/delphi/src/Thrift.Protocol.JSON.pas
+++ b/lib/delphi/src/Thrift.Protocol.JSON.pas
@@ -48,7 +48,7 @@
     type
       TFactory = class( TInterfacedObject, IProtocolFactory)
       public
-        function GetProtocol( trans: ITransport): IProtocol;
+        function GetProtocol( const trans: ITransport): IProtocol;
       end;
 
   private
@@ -126,12 +126,12 @@
 
     // Push/pop a new JSON context onto/from the stack.
     procedure ResetContextStack;
-    procedure PushContext( aCtx : TJSONBaseContext);
+    procedure PushContext( const aCtx : TJSONBaseContext);
     procedure PopContext;
 
   public
     // TJSONProtocolImpl Constructor
-    constructor Create( aTrans : ITransport);
+    constructor Create( const aTrans : ITransport);
     destructor Destroy;   override;
 
   protected
@@ -148,11 +148,11 @@
 
     // Write the bytes in array buf as a JSON characters, escaping as needed
     procedure WriteJSONString( const b : TBytes);  overload;
-    procedure WriteJSONString( str : string);  overload;
+    procedure WriteJSONString( const str : string);  overload;
 
     // Write out number as a JSON value. If the context dictates so, it will be
     // wrapped in quotes to output as a JSON string.
-    procedure WriteJSONInteger( num : Int64);
+    procedure WriteJSONInteger( const num : Int64);
 
     // Write out a double as a JSON value. If it is NaN or infinity or if the
     // context dictates escaping, Write out as JSON string.
@@ -168,25 +168,25 @@
 
   public
     // IProtocol
-    procedure WriteMessageBegin( aMsg : IMessage); override;
+    procedure WriteMessageBegin( const aMsg : IMessage); override;
     procedure WriteMessageEnd; override;
-    procedure WriteStructBegin(struc: IStruct); override;
+    procedure WriteStructBegin( const struc: IStruct); override;
     procedure WriteStructEnd; override;
-    procedure WriteFieldBegin(field: IField); override;
+    procedure WriteFieldBegin( const field: IField); override;
     procedure WriteFieldEnd; override;
     procedure WriteFieldStop; override;
-    procedure WriteMapBegin(map: IMap); override;
+    procedure WriteMapBegin( const map: IMap); override;
     procedure WriteMapEnd; override;
-    procedure WriteListBegin( list: IList); override;
+    procedure WriteListBegin( const list: IList); override;
     procedure WriteListEnd(); override;
-    procedure WriteSetBegin( set_: ISet ); override;
+    procedure WriteSetBegin( const set_: ISet ); override;
     procedure WriteSetEnd(); override;
     procedure WriteBool( b: Boolean); override;
     procedure WriteByte( b: ShortInt); override;
     procedure WriteI16( i16: SmallInt); override;
     procedure WriteI32( i32: Integer); override;
-    procedure WriteI64( i64: Int64); override;
-    procedure WriteDouble( d: Double); override;
+    procedure WriteI64( const i64: Int64); override;
+    procedure WriteDouble( const d: Double); override;
     procedure WriteString( const s: string );   override;
     procedure WriteBinary( const b: TBytes); override;
     //
@@ -290,7 +290,7 @@
 //--- TJSONProtocolImpl ----------------------
 
 
-function TJSONProtocolImpl.TFactory.GetProtocol( trans: ITransport): IProtocol;
+function TJSONProtocolImpl.TFactory.GetProtocol( const trans: ITransport): IProtocol;
 begin
   result := TJSONProtocolImpl.Create(trans);
 end;
@@ -455,7 +455,7 @@
 end;
 
 
-constructor TJSONProtocolImpl.Create( aTrans : ITransport);
+constructor TJSONProtocolImpl.Create( const aTrans : ITransport);
 begin
   inherited Create( aTrans);
 
@@ -487,7 +487,7 @@
 end;
 
 
-procedure TJSONProtocolImpl.PushContext( aCtx : TJSONBaseContext);
+procedure TJSONProtocolImpl.PushContext( const aCtx : TJSONBaseContext);
 begin
   FContextStack.Push( FContext);
   FContext := aCtx;
@@ -528,7 +528,7 @@
 end;
 
 
-procedure TJSONProtocolImpl.WriteJSONString( str : string);
+procedure TJSONProtocolImpl.WriteJSONString( const str : string);
 begin
   WriteJSONString( SysUtils.TEncoding.UTF8.GetBytes( str));
 end;
@@ -575,7 +575,7 @@
 end;
 
 
-procedure TJSONProtocolImpl.WriteJSONInteger( num : Int64);
+procedure TJSONProtocolImpl.WriteJSONInteger( const num : Int64);
 var str : String;
     escapeNum : Boolean;
 begin
@@ -676,7 +676,7 @@
 end;
 
 
-procedure TJSONProtocolImpl.WriteMessageBegin( aMsg : IMessage);
+procedure TJSONProtocolImpl.WriteMessageBegin( const aMsg : IMessage);
 begin
   ResetContextStack;  // THRIFT-1473
 
@@ -695,7 +695,7 @@
 end;
 
 
-procedure TJSONProtocolImpl.WriteStructBegin( struc: IStruct);
+procedure TJSONProtocolImpl.WriteStructBegin( const struc: IStruct);
 begin
   WriteJSONObjectStart;
 end;
@@ -707,7 +707,7 @@
 end;
 
 
-procedure TJSONProtocolImpl.WriteFieldBegin( field : IField);
+procedure TJSONProtocolImpl.WriteFieldBegin( const field : IField);
 begin
   WriteJSONInteger(field.ID);
   WriteJSONObjectStart;
@@ -726,7 +726,7 @@
   // nothing to do
 end;
 
-procedure TJSONProtocolImpl.WriteMapBegin( map: IMap);
+procedure TJSONProtocolImpl.WriteMapBegin( const map: IMap);
 begin
   WriteJSONArrayStart;
   WriteJSONString( GetTypeNameForTypeID( map.KeyType));
@@ -743,7 +743,7 @@
 end;
 
 
-procedure TJSONProtocolImpl.WriteListBegin( list: IList);
+procedure TJSONProtocolImpl.WriteListBegin( const list: IList);
 begin
   WriteJSONArrayStart;
   WriteJSONString( GetTypeNameForTypeID( list.ElementType));
@@ -757,7 +757,7 @@
 end;
 
 
-procedure TJSONProtocolImpl.WriteSetBegin( set_: ISet);
+procedure TJSONProtocolImpl.WriteSetBegin( const set_: ISet);
 begin
   WriteJSONArrayStart;
   WriteJSONString( GetTypeNameForTypeID( set_.ElementType));
@@ -792,12 +792,12 @@
   WriteJSONInteger( i32);
 end;
 
-procedure TJSONProtocolImpl.WriteI64( i64: Int64);
+procedure TJSONProtocolImpl.WriteI64( const i64: Int64);
 begin
   WriteJSONInteger(i64);
 end;
 
-procedure TJSONProtocolImpl.WriteDouble( d: Double);
+procedure TJSONProtocolImpl.WriteDouble( const d: Double);
 begin
   WriteJSONDouble( d);
 end;