Index: pyglet/window/xlib/__init__.py
===================================================================
--- pyglet/window/xlib/__init__.py.orig
+++ pyglet/window/xlib/__init__.py
@@ -352,6 +352,9 @@ class XlibWindow(BaseWindow):
         # Set caption
         self.set_caption(self._caption)
 
+        # Set WM_CLASS for modern desktop environments
+        self.set_wm_class(self._caption)        
+
         # this is supported by some compositors (ie gnome-shell), and more to come
         # see: http://standards.freedesktop.org/wm-spec/wm-spec-latest.html#idp6357888
         _NET_WM_BYPASS_COMPOSITOR_HINT_ON = c_ulong(int(self._fullscreen))
@@ -513,6 +516,19 @@ class XlibWindow(BaseWindow):
         self._set_text_property('_NET_WM_NAME', caption)
         self._set_text_property('_NET_WM_ICON_NAME', caption)
 
+    def set_wm_class(self, name):
+        # WM_CLASS can only contain Ascii characters
+        try:
+            name = name.encode('ascii')
+        except UnicodeEncodeError:
+            name = "pyglet"
+
+        hints = xlib.XAllocClassHint()
+        hints.contents.res_class = asbytes(name)
+        hints.contents.res_name = asbytes(name.lower())
+        xlib.XSetClassHint(self._x_display, self._window, hints.contents)
+        xlib.XFree(hints)
+
     def get_caption(self):
         return self._caption