diff --git a/ChangeLog b/ChangeLog
index 637a2c8..106fc28 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2011-06-01  Wolfgang Lux  <wolfgang.lux@gmail.com>
+
+	* Headers/x11/XGServerWindow.h (GSMaxWMProtocols, _gswindow_device_t):
+	Enlarge protocol array to make space for the _NET_WM_SYNC_REQUEST
+	protocol atom.
+
+	* Source/x11/XGServerWindow.m (_setSupportedWMProtocols:): Add
+	assertion to catch out of bounds errors in the future.
+
 2011-05-27 13:53  David Chisnall <theraven@gna.org>
 
 	* libs/back/trunk/Source/x11/XGServerWindow.m: Call NSZoneFree() on
diff --git a/Headers/x11/XGServerWindow.h b/Headers/x11/XGServerWindow.h
index 7e6f004..0ce9efd 100644
--- a/Headers/x11/XGServerWindow.h
+++ b/Headers/x11/XGServerWindow.h
@@ -72,6 +72,8 @@ typedef struct {
 #define WMFHideOtherApplications		10
 #define WMFHideApplication			12
 
+#define GSMaxWMProtocols 5
+
 /* Graphics Driver protocol. Setup in [NSGraphicsContext-contextDevice:] */
 enum {
   GDriverHandlesBacking = 1,
@@ -109,7 +111,7 @@ typedef struct _gswindow_device_t {
   int			xoff;
   int			yoff;
   int			boff;
-  Atom			protocols[4];
+  Atom			protocols[GSMaxWMProtocols];
   int			numProtocols;
   XIC                   ic;
   void                  *gdriver;      /* gdriver ident. Managed by gdriver */
diff --git a/Source/x11/XGServerWindow.m b/Source/x11/XGServerWindow.m
index 2e3eabf..eca8729 100644
--- a/Source/x11/XGServerWindow.m
+++ b/Source/x11/XGServerWindow.m
@@ -1456,6 +1456,9 @@ _get_next_prop_new_event(Display *display, XEvent *event, char *arg)
     {
       window->protocols[window->numProtocols++] = generic.miniaturize_atom;
     }
+  NSAssert1(window->numProtocols <= GSMaxWMProtocols,
+	    @"Too many protocols (%d > GSMaxWMProtocols)",
+	    window->numProtocols);
   XSetWMProtocols(dpy, window->ident, window->protocols, window->numProtocols);
 }