diff --git a/src/x11_init.c b/src/x11_init.c
index d7ee00dc..eba89a77 100644
--- a/src/x11_init.c
+++ b/src/x11_init.c
@@ -434,6 +434,7 @@ static GLboolean initDisplay(void)
 
     _glfw.x11.screen = DefaultScreen(_glfw.x11.display);
     _glfw.x11.root = RootWindow(_glfw.x11.display, _glfw.x11.screen);
+    _glfw.x11.context = XUniqueContext();
 
     // Find or create window manager atoms
     _glfw.x11.WM_STATE = XInternAtom(_glfw.x11.display, "WM_STATE", False);
diff --git a/src/x11_platform.h b/src/x11_platform.h
index 03ab5f38..36d887b4 100644
--- a/src/x11_platform.h
+++ b/src/x11_platform.h
@@ -108,6 +108,7 @@ typedef struct _GLFWlibraryX11
 
     // Invisible cursor for hidden cursor mode
     Cursor          cursor;
+    XContext        context;
 
     // Window manager atoms
     Atom            WM_STATE;
diff --git a/src/x11_window.c b/src/x11_window.c
index 0357bae4..1b834fd2 100644
--- a/src/x11_window.c
+++ b/src/x11_window.c
@@ -154,6 +154,11 @@ static GLboolean createWindow(_GLFWwindow* window,
                             (unsigned char*) &hints,
                             sizeof(MotifWmHints) / sizeof(long));
         }
+
+        XSaveContext(_glfw.x11.display,
+                     window->x11.handle,
+                     _glfw.x11.context,
+                     (XPointer) window);
     }
 
     if (window->monitor && !_glfw.x11.hasEWMH)
@@ -461,13 +466,15 @@ _GLFWwindow* _glfwFindWindowByHandle(Window handle)
 {
     _GLFWwindow* window;
 
-    for (window = _glfw.windowListHead;  window;  window = window->next)
+    if (XFindContext(_glfw.x11.display,
+                     handle,
+                     _glfw.x11.context,
+                     (XPointer*) &window) != 0)
     {
-        if (window->x11.handle == handle)
-            return window;
+        return NULL;
     }
 
-    return NULL;
+    return window;
 }
 
 // Process the specified X event
@@ -897,6 +904,7 @@ void _glfwPlatformDestroyWindow(_GLFWwindow* window)
 
     if (window->x11.handle)
     {
+        XDeleteContext(_glfw.x11.display, window->x11.handle, _glfw.x11.context);
         XUnmapWindow(_glfw.x11.display, window->x11.handle);
         XDestroyWindow(_glfw.x11.display, window->x11.handle);
         window->x11.handle = (Window) 0;