diff --git a/examples/Makefile b/examples/Makefile
index 3f10185..771a4c7 100644
--- a/examples/Makefile
+++ b/examples/Makefile
@@ -18,7 +18,7 @@ $(EXAMPLES): %: %.c $(STATIC)
 	$(CC) $(CFLAGS) $< -o $@ $(STATIC)
 
 cluster: cluster.c $(STATIC)
-	$(CC) $(CFLAGS) $< -o $@ $(STATIC) $(shell pkg-config --cflags --libs cairo x11) -lm
+	$(CC) $(CFLAGS) $< -o $@ $(STATIC) $(shell pkg-config --cflags --libs cairo x11) -lXext -lm
 
 view: view.c $(STATIC)
 	$(CC) $(CFLAGS) $< -o $@ $(STATIC) -lncurses
diff --git a/examples/cluster.c b/examples/cluster.c
index 836a216..633eba8 100644
--- a/examples/cluster.c
+++ b/examples/cluster.c
@@ -6,6 +6,8 @@
 #include <X11/Xlib.h>
 #include <X11/Xatom.h>
 #include <X11/Xutil.h>
+#include <X11/extensions/Xdbe.h>
+
 #include <cairo.h>
 #include <cairo-xlib.h>
 
@@ -228,6 +230,7 @@ int main(int argc, char **argv) {
     Display *display;
     Window win;
     Pixmap bg;
+    XdbeBackBuffer buf;
     GC gc;
     fd_set rfds, rready;
 
@@ -237,6 +240,8 @@ int main(int argc, char **argv) {
         width  = 1024,
         height = 480;
 
+    int major, minor;
+
     XGCValues values = {
         .foreground         = 0x000000,
         .background         = 0xffffff,
@@ -252,6 +257,11 @@ int main(int argc, char **argv) {
     if ((display = XOpenDisplay(NULL)) == NULL)
         exit(1);
 
+    if (XdbeQueryExtension(display, &major, &minor))
+        printf("Xdbe %d.%d supported\n", major, minor);
+    else
+        exit(1);
+
     fd  = hexagram_can_if_fd(can_if);
     fd2 = ConnectionNumber(display);