diff --git a/src/jtk/jtk.c b/src/jtk/jtk.c
index a6c6db7..621f15d 100644
--- a/src/jtk/jtk.c
+++ b/src/jtk/jtk.c
@@ -96,9 +96,10 @@ static Bool wait_for_notify(Display * display, XEvent * event, XPointer arg)
     return (event->type == MapNotify) && (event->xmap.window == (Window)arg);
 }
 
-void * jtk_window_create()
+bool jtk_window_create(uint64_t * window_handle)
 {
     XEvent event;
+    bool success;
 
     XLockDisplay(g_display);
     Window window = XCreateWindow(g_display,
@@ -112,40 +113,42 @@ void * jtk_window_create()
         /* Disable the window close button. */
         Atom wm_delete_window_atom = XInternAtom(g_display, "WM_DELETE_WINDOW", False);
         XSetWMProtocols(g_display, window, &wm_delete_window_atom, 1);
+        success = true;
+        *window_handle = (uint64_t)window;
     }
     else
     {
         fprintf(stderr, "glXMakeCurrent() failure\n");
         XDestroyWindow(g_display, window);
-        window = NULL;
+        success = false;
     }
 
     XUnlockDisplay(g_display);
 
-    return (void *)window;
+    return success;
 }
 
-void jtk_window_swap_buffers(void * window)
+void jtk_window_swap_buffers(uint64_t window_handle)
 {
     XLockDisplay(g_display);
-    glXSwapBuffers(g_display, (Window)window);
+    glXSwapBuffers(g_display, (Window)window_handle);
     XUnlockDisplay(g_display);
 }
 
-void jtk_window_close(void * window)
+void jtk_window_close(uint64_t window_handle)
 {
     XLockDisplay(g_display);
-    XDestroyWindow(g_display, (Window)window);
+    XDestroyWindow(g_display, (Window)window_handle);
     XUnlockDisplay(g_display);
 }
 
-void jtk_window_set_title(void * window, const char * title)
+void jtk_window_set_title(uint64_t window_handle, const char * title)
 {
     XLockDisplay(g_display);
     XTextProperty title_property;
     if (XStringListToTextProperty((char **)&title, 1, &title_property) != 0)
     {
-        XSetTextProperty(g_display, (Window)window, &title_property, XA_WM_NAME);
+        XSetTextProperty(g_display, (Window)window_handle, &title_property, XA_WM_NAME);
         XFree(title_property.value);
     }
     XUnlockDisplay(g_display);
@@ -164,7 +167,7 @@ void jtk_window_set_title(void * window, const char * title)
  * @param height
  *   Icon height.
  */
-void jtk_window_set_icon(void * window, const uint8_t * data,
+void jtk_window_set_icon(uint64_t window_handle, const uint8_t * data,
         size_t width, size_t height)
 {
     XLockDisplay(g_display);
@@ -182,8 +185,9 @@ void jtk_window_set_icon(void * window, const uint8_t * data,
             *dest++ = *src++;
         }
     }
-    XChangeProperty(g_display, (Window)window, net_wm_icon_atom, XA_CARDINAL,
-            32, PropModeReplace, (uint8_t *)property_data, property_size);
+    XChangeProperty(g_display, (Window)window_handle, net_wm_icon_atom,
+            XA_CARDINAL, 32, PropModeReplace, (uint8_t *)property_data,
+            property_size);
     XFlush(g_display);
     free(property_data);
     XUnlockDisplay(g_display);
diff --git a/src/jtk/window.d b/src/jtk/window.d
index 651ab1d..77abdc4 100644
--- a/src/jtk/window.d
+++ b/src/jtk/window.d
@@ -2,20 +2,23 @@ module jtk.window;
 
 import std.string;
 
-private extern(C) void * jtk_window_create();
-private extern(C) void jtk_window_swap_buffers(void * window);
-private extern(C) void jtk_window_close(void * window);
-private extern(C) void jtk_window_set_title(void * window, const char * title);
-private extern(C) void jtk_window_set_icon(void * window, const ubyte * data,
+private extern(C) bool jtk_window_create(ulong * window);
+private extern(C) void jtk_window_swap_buffers(ulong window);
+private extern(C) void jtk_window_close(ulong window);
+private extern(C) void jtk_window_set_title(ulong window, const char * title);
+private extern(C) void jtk_window_set_icon(ulong window, const ubyte * data,
         size_t width, size_t height);
 
 class Window
 {
-    private void * m_window;
+    private ulong m_window;
 
     this()
     {
-        m_window = jtk_window_create();
+        if (!jtk_window_create(&m_window))
+        {
+            /* TODO */
+        }
     }
 
     void close()