diff --git a/kwin/atoms.cpp b/kwin/atoms.cpp
index cb11edd6..60a3024d 100644
--- a/kwin/atoms.cpp
+++ b/kwin/atoms.cpp
@@ -82,9 +82,6 @@ Atoms::Atoms()
     atoms[n] = &net_wm_take_activity;
     names[n++] = (char*) "_NET_WM_TAKE_ACTIVITY";
 
-    atoms[n] = &net_wm_window_opacity;
-    names[n++] = (char*) "_NET_WM_WINDOW_OPACITY";
-
     Atom fake;
     atoms[n] = &fake;
     names[n++] = (char *) "_DT_SM_WINDOW_INFO";
diff --git a/kwin/atoms.h b/kwin/atoms.h
index 23419128..6368d624 100644
--- a/kwin/atoms.h
+++ b/kwin/atoms.h
@@ -51,7 +51,6 @@ public:
     Atom net_wm_user_time;
     Atom kde_net_wm_user_creation_time;
     Atom net_wm_take_activity;
-    Atom net_wm_window_opacity;
     Atom xdnd_aware;
     Atom xdnd_position;
     Atom net_frame_extents;