diff --git a/hw/xnest/Color.c b/hw/xnest/Color.c
index 517452047..76012ddbf 100644
--- a/hw/xnest/Color.c
+++ b/hw/xnest/Color.c
@@ -38,6 +38,8 @@ is" without express or implied warranty.
 #include "XNWindow.h"
 #include "Args.h"
 
+#include <xcb/xcb_icccm.h>
+
 DevPrivateKeyRec xnestColormapPrivateKeyRec;
 
 static DevPrivateKeyRec cmapScrPrivateKeyRec;
@@ -223,22 +225,10 @@ xnestSetInstalledColormapWindows(ScreenPtr pScreen)
     if (!xnestSameInstalledColormapWindows(icws.windows, icws.numWindows)) {
         free(xnestOldInstalledColormapWindows);
 
-#ifdef _XSERVER64
-        {
-            int i;
-            Window64 *windows = xallocarray(numWindows, sizeof(Window64));
-
-            for (i = 0; i < numWindows; ++i)
-                windows[i] = icws.windows[i];
-            XSetWMColormapWindows(xnestDisplay,
-                                  xnestDefaultWindows[pScreen->myNum], windows,
+        xnest_wm_colormap_windows(xnestUpstreamInfo.conn,
+                                  xnestDefaultWindows[pScreen->myNum],
+                                  icws.windows,
                                   numWindows);
-            free(windows);
-        }
-#else
-        XSetWMColormapWindows(xnestDisplay, xnestDefaultWindows[pScreen->myNum],
-                              icws.windows, numWindows);
-#endif
 
         xnestOldInstalledColormapWindows = icws.windows;
         xnestNumOldInstalledColormapWindows = icws.numWindows;
@@ -280,19 +270,10 @@ xnestSetScreenSaverColormapWindow(ScreenPtr pScreen)
 {
     free(xnestOldInstalledColormapWindows);
 
-#ifdef _XSERVER64
-    {
-        Window64 window;
-
-        window = xnestScreenSaverWindows[pScreen->myNum];
-        XSetWMColormapWindows(xnestDisplay, xnestDefaultWindows[pScreen->myNum],
-                              &window, 1);
-        xnestScreenSaverWindows[pScreen->myNum] = window;
-    }
-#else
-    XSetWMColormapWindows(xnestDisplay, xnestDefaultWindows[pScreen->myNum],
-                          &xnestScreenSaverWindows[pScreen->myNum], 1);
-#endif                          /* _XSERVER64 */
+    xnest_wm_colormap_windows(xnestUpstreamInfo.conn,
+                              xnestDefaultWindows[pScreen->myNum],
+                              &xnestScreenSaverWindows[pScreen->myNum],
+                              1);
 
     xnestOldInstalledColormapWindows = NULL;
     xnestNumOldInstalledColormapWindows = 0;
diff --git a/hw/xnest/meson.build b/hw/xnest/meson.build
index ccff44867..e2a978b83 100644
--- a/hw/xnest/meson.build
+++ b/hw/xnest/meson.build
@@ -24,6 +24,7 @@ x11_xcb_dep = dependency('x11-xcb', required: true)
 xcb_dep = dependency('xcb', required: true)
 xcb_aux_dep = dependency('xcb-aux', required: true)
 xcb_shape_dep = dependency('xcb-shape', required: true)
+xcb_icccm_dep = dependency('xcb-icccm', required: true)
 
 executable(
     'Xnest',
@@ -35,6 +36,7 @@ executable(
         xcb_dep,
         xcb_aux_dep,
         xcb_shape_dep,
+        xcb_icccm_dep,
         x11_xcb_dep,
     ],
     link_with: [
diff --git a/hw/xnest/xcb.c b/hw/xnest/xcb.c
index 83284361d..41f6dbfb8 100644
--- a/hw/xnest/xcb.c
+++ b/hw/xnest/xcb.c
@@ -5,6 +5,7 @@
 #include <dix-config.h>
 
 #include <xcb/xcb.h>
+#include <xcb/xcb_icccm.h>
 
 #include <X11/X.h>
 #include <X11/Xdefs.h>
@@ -42,3 +43,32 @@ uint32_t xnest_upstream_gc(GCPtr pGC) {
 
     return priv->gc;
 }
+
+const char WM_COLORMAP_WINDOWS[] = "WM_COLORMAP_WINDOWS";
+
+void xnest_wm_colormap_windows(
+    xcb_connection_t *conn,
+    xcb_window_t w,
+    xcb_window_t *windows,
+    int count)
+{
+    xcb_intern_atom_reply_t *reply = xcb_intern_atom_reply(
+        conn,
+        xcb_intern_atom(
+            conn, 0,
+            sizeof(WM_COLORMAP_WINDOWS)-1,
+            WM_COLORMAP_WINDOWS),
+        NULL);
+
+    if (!reply)
+        return;
+
+    xcb_icccm_set_wm_colormap_windows_checked(
+        conn,
+        w,
+        reply->atom,
+        count,
+        (xcb_window_t*)windows);
+
+    free(reply);
+}
diff --git a/hw/xnest/xnest-xcb.h b/hw/xnest/xnest-xcb.h
index 3c35e04dc..a924e2575 100644
--- a/hw/xnest/xnest-xcb.h
+++ b/hw/xnest/xnest-xcb.h
@@ -22,4 +22,7 @@ void xnest_upstream_setup(void);
 /* retrieve upstream GC XID for our xserver GC */
 uint32_t xnest_upstream_gc(GCPtr pGC);
 
+void xnest_wm_colormap_windows(xcb_connection_t *conn, xcb_window_t w,
+                               xcb_window_t *windows, int count);
+
 #endif /* __XNEST__XCB_H */