diff --git a/lib/modules/Protocols.pmod/X.pmod/_Xlib.pmod b/lib/modules/Protocols.pmod/X.pmod/_Xlib.pmod
index c0cce15cfb5ac782200db45388bcfcdc2dfa4cf8..a546572a6d748edc55733fbe7a0368e932ca8b25 100644
--- a/lib/modules/Protocols.pmod/X.pmod/_Xlib.pmod
+++ b/lib/modules/Protocols.pmod/X.pmod/_Xlib.pmod
@@ -163,6 +163,79 @@ array(string) error_codes =
   "Implementation"	/* server is defective */
 });
 
+/* FIXME: Could the XA_-prefix be removed, like for the constants? */
+array(string) predefined_atoms =
+({ "Foo", // ignored
+   "XA_PRIMARY",
+   "XA_SECONDARY",
+   "XA_ARC",
+   "XA_ATOM",
+   "XA_BITMAP",
+   "XA_CARDINAL",
+   "XA_COLORMAP",
+   "XA_CURSOR",
+   "XA_CUT_BUFFER0",
+   "XA_CUT_BUFFER1",
+   "XA_CUT_BUFFER2",
+   "XA_CUT_BUFFER3",
+   "XA_CUT_BUFFER4",
+   "XA_CUT_BUFFER5",
+   "XA_CUT_BUFFER6",
+   "XA_CUT_BUFFER7",
+   "XA_DRAWABLE",
+   "XA_FONT",
+   "XA_INTEGER",
+   "XA_PIXMAP",
+   "XA_POINT",
+   "XA_RECTANGLE",
+   "XA_RESOURCE_MANAGER",
+   "XA_RGB_COLOR_MAP",
+   "XA_RGB_BEST_MAP",
+   "XA_RGB_BLUE_MAP",
+   "XA_RGB_DEFAULT_MAP",
+   "XA_RGB_GRAY_MAP",
+   "XA_RGB_GREEN_MAP",
+   "XA_RGB_RED_MAP",
+   "XA_STRING",
+   "XA_VISUALID",
+   "XA_WINDOW",
+   "XA_WM_COMMAND",
+   "XA_WM_HINTS",
+   "XA_WM_CLIENT_MACHINE",
+   "XA_WM_ICON_NAME",
+   "XA_WM_ICON_SIZE",
+   "XA_WM_NAME",
+   "XA_WM_NORMAL_HINTS",
+   "XA_WM_SIZE_HINTS",
+   "XA_WM_ZOOM_HINTS",
+   "XA_MIN_SPACE",
+   "XA_NORM_SPACE",
+   "XA_MAX_SPACE",
+   "XA_END_SPACE",
+   "XA_SUPERSCRIPT_X",
+   "XA_SUPERSCRIPT_Y",
+   "XA_SUBSCRIPT_X",
+   "XA_SUBSCRIPT_Y",
+   "XA_UNDERLINE_POSITION",
+   "XA_UNDERLINE_THICKNESS",
+   "XA_STRIKEOUT_ASCENT",
+   "XA_STRIKEOUT_DESCENT",
+   "XA_ITALIC_ANGLE",
+   "XA_X_HEIGHT",
+   "XA_QUAD_WIDTH",
+   "XA_WEIGHT",
+   "XA_POINT_SIZE",
+   "XA_RESOLUTION",
+   "XA_COPYRIGHT",
+   "XA_NOTICE",
+   "XA_FONT_NAME",
+   "XA_FAMILY_NAME",
+   "XA_FULL_NAME",
+   "XA_CAP_HEIGHT",
+   "XA_WM_CLASS",
+   "XA_WM_TRANSIENT_FOR"
+});
+
 array(string) visual_classes =
 ({
   "StaticGray",
@@ -172,3 +245,4 @@ array(string) visual_classes =
   "TrueColor",
   "DirectColor",
 });
+