diff --git a/packages/winunits-jedi/src/jwaactivex.pas b/packages/winunits-jedi/src/jwaactivex.pas
index 2e0b7ca2a8..13839a8b33 100644
--- a/packages/winunits-jedi/src/jwaactivex.pas
+++ b/packages/winunits-jedi/src/jwaactivex.pas
@@ -276,16 +276,16 @@ type
 
   IStream = interface(ISequentialStream)
     ['{0000000C-0000-0000-C000-000000000046}']
-    function Seek(dlibMove: Largeint; dwOrigin: Longint;
-      out libNewPosition: Largeint): HRESULT; stdcall;
-    function SetSize(libNewSize: Largeint): HRESULT; stdcall;
-    function CopyTo(stm: IStream; cb: Largeint; out cbRead: Largeint;
-      out cbWritten: Largeint): HRESULT; stdcall;
+    function Seek(dlibMove: qword; dwOrigin: Longint;
+      out libNewPosition: qword): HRESULT; stdcall;
+    function SetSize(libNewSize: qword): HRESULT; stdcall;
+    function CopyTo(stm: IStream; cb: qword; out cbRead: qword;
+      out cbWritten: qword): HRESULT; stdcall;
     function Commit(grfCommitFlags: Longint): HRESULT; stdcall;
     function Revert: HRESULT; stdcall;
-    function LockRegion(libOffset: Largeint; cb: Largeint;
+    function LockRegion(libOffset: qword; cb: qword;
       dwLockType: Longint): HRESULT; stdcall;
-    function UnlockRegion(libOffset: Largeint; cb: Largeint;
+    function UnlockRegion(libOffset: qword; cb: qword;
       dwLockType: Longint): HRESULT; stdcall;
     function Stat(out statstg: TStatStg; grfStatFlag: Longint): HRESULT; stdcall;
     function Clone(out stm: IStream): HRESULT; stdcall;
diff --git a/rtl/objpas/classes/classesh.inc b/rtl/objpas/classes/classesh.inc
index c9de0dcdce..84e9e0bd48 100644
--- a/rtl/objpas/classes/classesh.inc
+++ b/rtl/objpas/classes/classesh.inc
@@ -1055,13 +1055,13 @@ type
     destructor Destroy; override;
     function Read(pv: Pointer; cb: DWORD; pcbRead: PDWORD): HResult; virtual; stdcall;
     function Write(pv: Pointer; cb: DWORD; pcbWritten: PDWORD): HResult; virtual; stdcall;
-    function Seek(dlibMove: Largeint; dwOrigin: Longint; out libNewPosition: Largeint): HResult; virtual; stdcall;
-    function SetSize(libNewSize: Largeint): HResult; virtual; stdcall;
-    function CopyTo(stm: IStream; cb: Largeint; out cbRead: Largeint; out cbWritten: Largeint): HResult; virtual; stdcall;
+    function Seek(dlibMove: LargeUint; dwOrigin: Longint; out libNewPosition: LargeUint): HResult; virtual; stdcall;
+    function SetSize(libNewSize: LargeUint): HResult; virtual; stdcall;
+    function CopyTo(stm: IStream; cb: LargeUint; out cbRead: LargeUint; out cbWritten: LargeUint): HResult; virtual; stdcall;
     function Commit(grfCommitFlags: Longint): HResult; virtual; stdcall;
     function Revert: HResult; virtual; stdcall;
-    function LockRegion(libOffset: Largeint; cb: Largeint; dwLockType: Longint): HResult; virtual; stdcall;
-    function UnlockRegion(libOffset: Largeint; cb: Largeint; dwLockType: Longint): HResult; virtual; stdcall;
+    function LockRegion(libOffset: LargeUint; cb: LargeUint; dwLockType: Longint): HResult; virtual; stdcall;
+    function UnlockRegion(libOffset: LargeUint; cb: LargeUint; dwLockType: Longint): HResult; virtual; stdcall;
     function Stat(out statstg: TStatStg; grfStatFlag: Longint): HResult; virtual; stdcall;
     function Clone(out stm: IStream): HResult; virtual; stdcall;
     property Stream: TStream read FStream;
diff --git a/rtl/objpas/classes/streams.inc b/rtl/objpas/classes/streams.inc
index 5fdbd1d0bc..fdb154ace0 100644
--- a/rtl/objpas/classes/streams.inc
+++ b/rtl/objpas/classes/streams.inc
@@ -1034,9 +1034,9 @@ begin
   Result := S_OK;
 end;
 
-function TStreamAdapter.Seek(dlibMove: Largeint; dwOrigin: Longint; out libNewPosition: Largeint): HResult; stdcall;
+function TStreamAdapter.Seek(dlibMove: LargeUint; dwOrigin: Longint; out libNewPosition: LargeUint): HResult; stdcall;
 var
-  newpos: Int64;
+  newpos: QWord;
 begin
   if m_bReverted then
     begin
@@ -1058,7 +1058,7 @@ begin
   Result := S_OK;
 end;
 
-function TStreamAdapter.SetSize(libNewSize: Largeint): HResult; stdcall;
+function TStreamAdapter.SetSize(libNewSize: LargeUint): HResult; stdcall;
 begin
   if m_bReverted then
     begin
@@ -1080,7 +1080,7 @@ begin
 end;
 
 
-function TStreamAdapter.CopyTo(stm: IStream; cb: Largeint; out cbRead: Largeint; out cbWritten: Largeint): HResult; stdcall;
+function TStreamAdapter.CopyTo(stm: IStream; cb: LargeUint; out cbRead: LargeUint; out cbWritten: Largeuint): HResult; stdcall;
 var
   sz: dword;
   buffer : array[0..1023] of byte;
@@ -1129,13 +1129,13 @@ begin
 end;
 
 
-function TStreamAdapter.LockRegion(libOffset: Largeint; cb: Largeint; dwLockType: Longint): HResult; stdcall;
+function TStreamAdapter.LockRegion(libOffset: LargeUint; cb: LargeUint; dwLockType: Longint): HResult; stdcall;
 begin
   Result := STG_E_INVALIDFUNCTION;
 end;
 
 
-function TStreamAdapter.UnlockRegion(libOffset: Largeint; cb: Largeint; dwLockType: Longint): HResult; stdcall;
+function TStreamAdapter.UnlockRegion(libOffset: LargeUint; cb: LargeUint; dwLockType: Longint): HResult; stdcall;
 begin
   Result := STG_E_INVALIDFUNCTION;
 end;
@@ -1190,9 +1190,9 @@ begin
   Check(FStream.Read(@Buffer, Count, @Result));
 end;
 
-function TProxyStream. Seek(const Offset: int64; Origin: TSeekOrigin): int64;
+function TProxyStream.Seek(const Offset: int64; Origin: TSeekOrigin): int64;
 begin
-  Check(FStream.Seek(Offset, ord(Origin), result));
+  Check(FStream.Seek(Offset, ord(Origin), QWord(result)));
 end;
 
 function TProxyStream.Write(const Buffer; Count: Longint): Longint;
diff --git a/rtl/objpas/types.pp b/rtl/objpas/types.pp
index 5ccebebc36..29d6e9347c 100644
--- a/rtl/objpas/types.pp
+++ b/rtl/objpas/types.pp
@@ -299,17 +299,13 @@ type
   end;
 
   IStream = interface(ISequentialStream) ['{0000000C-0000-0000-C000-000000000046}']
-     function Seek(dlibMove : LargeInt; dwOrigin : Longint;
-       out libNewPosition : LargeInt) : HResult;stdcall;
-     function SetSize(libNewSize : LargeInt) : HRESULT;stdcall;
-     function CopyTo(stm: IStream;cb : LargeInt;out cbRead : LargeInt;
-       out cbWritten : LargeInt) : HRESULT;stdcall;
+     function Seek(dlibMove : LargeUInt; dwOrigin : Longint; out libNewPosition : LargeUInt) : HResult;stdcall;
+     function SetSize(libNewSize : LargeUInt) : HRESULT;stdcall;
+     function CopyTo(stm: IStream;cb : LargeUInt;out cbRead : LargeUInt; out cbWritten : LargeUInt) : HRESULT;stdcall;
      function Commit(grfCommitFlags : Longint) : HRESULT;stdcall;
      function Revert : HRESULT;stdcall;
-     function LockRegion(libOffset : LargeInt;cb : LargeInt;
-       dwLockType : Longint) : HRESULT;stdcall;
-     function UnlockRegion(libOffset : LargeInt;cb : LargeInt;
-       dwLockType : Longint) : HRESULT;stdcall;
+     function LockRegion(libOffset : LargeUInt;cb : LargeUInt; dwLockType : Longint) : HRESULT;stdcall;
+     function UnlockRegion(libOffset : LargeUInt;cb : LargeUInt; dwLockType : Longint) : HRESULT;stdcall;
      Function Stat(out statstg : TStatStg;grfStatFlag : Longint) : HRESULT;stdcall;
      function Clone(out stm : IStream) : HRESULT;stdcall;
   end;