diff --git a/dglOpenGL.pas b/dglOpenGL.pas
index a079bea..0663952 100644
--- a/dglOpenGL.pas
+++ b/dglOpenGL.pas
@@ -171,7 +171,7 @@ interface
 
 uses
   {$IFDEF FPC}{$IFDEF DARWIN}dynlibs,{$ENDIF}{$ENDIF}  // LoadLibrary functions
-  SysUtils
+  SysUtils, Types
   {$IFDEF DGL_WIN}, Windows{$ENDIF}
   {$IFDEF DGL_64BIT} ,math {$ENDIF}
   {$IFDEF DGL_LINUX}, X, XLib, XUtil{$ENDIF}