diff --git a/src/RestJsonUtils.pas b/src/RestJsonUtils.pas
index f46a587..75c6863 100644
--- a/src/RestJsonUtils.pas
+++ b/src/RestJsonUtils.pas
@@ -30,7 +30,7 @@   TJsonUtil = class
 function JavaToDelphiDateTime(const dt: int64): TDateTime;
 function DelphiToJavaDateTime(const dt: TDateTime): int64;
 function ISO8601DateToJavaDateTime(const str: String; var ms: Int64): Boolean;
-function ISO8601DateToDelphiDateTime(const str: string; var dt: TDateTime): Boolean;
+function ISO8601DateToDelphiDateTime(const str: String; var dt: TDateTime): Boolean;
 function DelphiDateTimeToISO8601Date(dt: TDateTime): string;
 
 implementation
@@ -356,9 +356,11 @@   TDateTimeInfo = record
 {$IFNDEF UNICODE}
   PSOChar = PWideChar;
   SOChar = WideChar;
+  SOString = WideString;
 {$ELSE}
   SOChar = Char;
   PSOChar = PChar;
+  SOString = String;
 {$ENDIF}
 
 var
@@ -383,7 +385,7 @@   TDateTimeInfo = record
 label
   error;
 begin
-  p := PSOChar(str);
+  p := PSOChar(SOString(str));
   sep := perhaps;
   state := stStart;
   pos := 0;
@@ -968,7 +970,7 @@   TDateTimeInfo = record
   Result := False;
 end;
 
-function ISO8601DateToDelphiDateTime(const str: string; var dt: TDateTime): Boolean;
+function ISO8601DateToDelphiDateTime(const str: String; var dt: TDateTime): Boolean;
 var
   ms: Int64;
 begin