diff --git a/lcl/interfaces/win32/win32wsstdctrls.pp b/lcl/interfaces/win32/win32wsstdctrls.pp
index f042b8d6a8..18f4977040 100644
--- a/lcl/interfaces/win32/win32wsstdctrls.pp
+++ b/lcl/interfaces/win32/win32wsstdctrls.pp
@@ -568,12 +568,15 @@ end;
 
 function  TWin32WSCustomComboBox.GetSelStart(const ACustomComboBox: TCustomComboBox): integer;
 begin
-  Result := Low(SendMessage(ACustomComboBox.Handle, CB_GETEDITSEL, Windows.WPARAM(nil), Windows.LPARAM(nil)));
+  SendMessage(ACustomComboBox.Handle, CB_GETEDITSEL, Windows.WPARAM(@Result), Windows.LPARAM(nil));
 end;
 
 function  TWin32WSCustomComboBox.GetSelLength(const ACustomComboBox: TCustomComboBox): integer;
+var
+  startPos, endPos: dword;
 begin
-  Result := SendMessage(ACustomComboBox.Handle, CB_GETEDITSEL, Windows.WPARAM(nil), Windows.LPARAM(nil));
+  SendMessage(ACustomComboBox.Handle, CB_GETEDITSEL, Windows.WPARAM(@startPos), Windows.LPARAM(@endPos));
+  Result := endPos - startPos;
 end;
 
 procedure TWin32WSCustomComboBox.SetStyle(const ACustomComboBox: TCustomComboBox; NewStyle: TComboBoxStyle);