diff --git a/components/lazutils/laz_xmlstreaming.pas b/components/lazutils/laz_xmlstreaming.pas
index 2636cab056..c6e05952b2 100644
--- a/components/lazutils/laz_xmlstreaming.pas
+++ b/components/lazutils/laz_xmlstreaming.pas
@@ -28,6 +28,12 @@ uses
   SysUtils, Classes, TypInfo, Laz2_DOM, Laz2_XMLWrite;
 
 type
+  {$IF FPC_FULLVERSION>30300}
+  TXMLObjectWriterString = RawByteString;
+  {$ELSE}
+  TXMLObjectWriterString = String;
+  {$ENDIF}
+
   TXMLObjectWriterStackElType = (elUnknown, elPropertyList, elChildrenList);
 
   TXMLObjectWriterStackEl = class
@@ -76,7 +82,7 @@ type
     procedure WriteInteger(Value: Int64); override;
     procedure WriteMethodName(const Name: String); override;
     procedure WriteSet(Value: LongInt; SetType: Pointer); override;
-    procedure WriteString(const Value: String); override;
+    procedure WriteString(const Value: TXMLObjectWriterString); override;
     procedure WriteWideString(const Value: WideString); override;
     procedure WriteSignature; override;
     {$IFDEF USE_NEW_READER_WRITER}
@@ -454,7 +460,7 @@ begin
   GetPropertyElement('set')['value'] := s;
 end;
 
-procedure TXMLObjectWriter.WriteString(const Value: String);
+procedure TXMLObjectWriter.WriteString(const Value: TXMLObjectWriterString);
 begin
   GetPropertyElement('string')['value'] := Value;
 end;
diff --git a/designer/designer.pp b/designer/designer.pp
index 7df3532e1d..9efe722c85 100644
--- a/designer/designer.pp
+++ b/designer/designer.pp
@@ -1544,9 +1544,9 @@ begin
       if tmpFieldN = 'Name' then
       begin
         if IsActUndo then
-          CompN := FUndoList[FUndoCurr].newVal
+          CompN := String(FUndoList[FUndoCurr].newVal)
         else
-          CompN := FUndoList[FUndoCurr].oldVal;
+          CompN := String(FUndoList[FUndoCurr].oldVal);
       end
       else
         CompN := FUndoList[FUndoCurr].compName;
diff --git a/lcl/lresources.pp b/lcl/lresources.pp
index ea2a3870f1..a394fd923f 100644
--- a/lcl/lresources.pp
+++ b/lcl/lresources.pp
@@ -226,6 +226,12 @@ type
   end;
   PLRSOWStackItem = ^TLRSOWStackItem;
 
+  {$IF FPC_FULLVERSION>30300}
+  TLazObjectWriterString = RawByteString;
+  {$ELSE}
+  TLazObjectWriterString = String;
+  {$ENDIF}
+
   { TLRSObjectWriter }
 
   TLRSObjectWriter = class(TAbstractObjectWriter)
@@ -291,7 +297,7 @@ type
     procedure WriteInteger(Value: Int64); override;
     procedure WriteMethodName(const Name: String); override;
     procedure WriteSet(Value: LongInt; SetType: Pointer); override;
-    procedure WriteString(const Value: String); override;
+    procedure WriteString(const Value: TLazObjectWriterString); override;
     procedure WriteWideString(const Value: WideString); override;
     procedure WriteUnicodeString(const Value: UnicodeString); override;
     procedure WriteVariant(const Value: Variant); override;
@@ -4957,7 +4963,7 @@ begin
   WriteStr('');
 end;
 
-procedure TLRSObjectWriter.WriteString(const Value: String);
+procedure TLRSObjectWriter.WriteString(const Value: TLazObjectWriterString);
 var
   i: Integer;
   b: Byte;
@@ -5013,7 +5019,7 @@ begin
     varcurrency:
       WriteCurrency(Value);
     varolestr, varstring:
-      WriteString(Value);
+      WriteString(String(Value));
     varboolean:
       WriteBoolean(Value);
     else