diff --git a/src/taskbar/task.c b/src/taskbar/task.c
index 066e13a..d79bc98 100644
--- a/src/taskbar/task.c
+++ b/src/taskbar/task.c
@@ -649,7 +649,8 @@ void set_task_state(Task *task, TaskState state)
     if (!task || state == TASK_UNDEFINED || state >= TASK_STATE_COUNT)
         return;
 
-    task_refresh_thumbnail(task);
+    if (!task->thumbnail)
+        task_refresh_thumbnail(task);
     taskbar_start_thumbnail_timer(TRUE);
 
     if (state == TASK_ACTIVE && task->current_state != state) {
diff --git a/src/taskbar/taskbar.c b/src/taskbar/taskbar.c
index 79b3c4b..81df2a8 100644
--- a/src/taskbar/taskbar.c
+++ b/src/taskbar/taskbar.c
@@ -365,7 +365,7 @@ void taskbar_start_thumbnail_timer(gboolean fast)
 {
     if (!panel_config.g_task.thumbnail_enabled)
         return;
-    change_timeout(&thumbnail_update_timer, 100, 10 * 1000, taskbar_update_thumbnails, (void*)(long)fast);
+    change_timeout(&thumbnail_update_timer, 500, 10 * 1000, taskbar_update_thumbnails, (void*)(long)fast);
 }
 
 void taskbar_init_fonts()
diff --git a/src/util/window.c b/src/util/window.c
index 321e665..9942dd6 100644
--- a/src/util/window.c
+++ b/src/util/window.c
@@ -388,7 +388,7 @@ cairo_surface_t *screenshot(Window win, size_t size)
 {
     cairo_surface_t *result = NULL;
     XWindowAttributes wa;
-    if (!XGetWindowAttributes(server.display, win, &wa) || wa.width <= 0 || wa.height <= 0)
+    if (!XGetWindowAttributes(server.display, win, &wa) || wa.width <= 0 || wa.height <= 0 || wa.map_state != IsViewable)
         goto err0;
 
     if (window_is_iconified(win))
@@ -448,7 +448,8 @@ cairo_surface_t *screenshot(Window win, size_t size)
         goto err4;
     }
 
-    if (window_is_iconified(win))
+    XGetWindowAttributes(server.display, win, &wa);
+    if (wa.map_state != IsViewable)
         goto err4;
 
     result = cairo_image_surface_create(CAIRO_FORMAT_RGB24, (int)tw, (int)th);
@@ -544,9 +545,7 @@ cairo_surface_t *get_window_thumbnail_cairo(Window win, int size)
 {
     static cairo_filter_t filter = CAIRO_FILTER_BEST;
     XWindowAttributes wa;
-    if (!XGetWindowAttributes(server.display, win, &wa))
-        return NULL;
-    if (window_is_iconified(win))
+    if (!XGetWindowAttributes(server.display, win, &wa) || wa.width <= 0 || wa.height <= 0 || wa.map_state != IsViewable)
         return NULL;
     int w, h;
     w = wa.width;
@@ -616,7 +615,7 @@ gboolean cairo_surface_is_blank(cairo_surface_t *image_surface)
 cairo_surface_t *get_window_thumbnail(Window win, int size)
 {
     cairo_surface_t *image_surface = NULL;
-    if (server.has_shm && server.composite_manager) {
+    if (0 && server.has_shm && server.composite_manager) {
         image_surface = screenshot(win, (size_t)size);
         if (image_surface && cairo_surface_is_blank(image_surface)) {
             cairo_surface_destroy(image_surface);