diff --git a/include/freetype/ftxf86.h b/include/freetype/ftxf86.h
index ae9ff076f..8c68afdcc 100644
--- a/include/freetype/ftxf86.h
+++ b/include/freetype/ftxf86.h
@@ -49,6 +49,9 @@ FT_BEGIN_HEADER
   /*   however, there are special cases (like in PDF devices) where it is  */
   /*   important to differentiate, in spite of FreeType's uniform API.     */
   /*                                                                       */
+  /*   This function is in the X11/xf86 namespace for historical reasons   */
+  /*   and in no way depends on that windowing system.                     */
+  /*                                                                       */
   /*************************************************************************/