diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c
index a8dbb3ef4e3c96..7c6225c84ba674 100644
--- a/drivers/gpu/drm/qxl/qxl_display.c
+++ b/drivers/gpu/drm/qxl/qxl_display.c
@@ -160,9 +160,35 @@ static int qxl_add_monitors_config_modes(struct drm_connector *connector,
 	*pwidth = head->width;
 	*pheight = head->height;
 	drm_mode_probed_add(connector, mode);
+	/* remember the last custom size for mode validation */
+	qdev->monitors_config_width = mode->hdisplay;
+	qdev->monitors_config_height = mode->vdisplay;
 	return 1;
 }
 
+static struct mode_size {
+	int w;
+	int h;
+} common_modes[] = {
+	{ 640,  480},
+	{ 720,  480},
+	{ 800,  600},
+	{ 848,  480},
+	{1024,  768},
+	{1152,  768},
+	{1280,  720},
+	{1280,  800},
+	{1280,  854},
+	{1280,  960},
+	{1280, 1024},
+	{1440,  900},
+	{1400, 1050},
+	{1680, 1050},
+	{1600, 1200},
+	{1920, 1080},
+	{1920, 1200}
+};
+
 static int qxl_add_common_modes(struct drm_connector *connector,
                                 unsigned pwidth,
                                 unsigned pheight)
@@ -170,29 +196,6 @@ static int qxl_add_common_modes(struct drm_connector *connector,
 	struct drm_device *dev = connector->dev;
 	struct drm_display_mode *mode = NULL;
 	int i;
-	struct mode_size {
-		int w;
-		int h;
-	} common_modes[] = {
-		{ 640,  480},
-		{ 720,  480},
-		{ 800,  600},
-		{ 848,  480},
-		{1024,  768},
-		{1152,  768},
-		{1280,  720},
-		{1280,  800},
-		{1280,  854},
-		{1280,  960},
-		{1280, 1024},
-		{1440,  900},
-		{1400, 1050},
-		{1680, 1050},
-		{1600, 1200},
-		{1920, 1080},
-		{1920, 1200}
-	};
-
 	for (i = 0; i < ARRAY_SIZE(common_modes); i++) {
 		mode = drm_cvt_mode(dev, common_modes[i].w, common_modes[i].h,
 				    60, false, false, false);
@@ -823,11 +826,22 @@ static int qxl_conn_get_modes(struct drm_connector *connector)
 static int qxl_conn_mode_valid(struct drm_connector *connector,
 			       struct drm_display_mode *mode)
 {
+	struct drm_device *ddev = connector->dev;
+	struct qxl_device *qdev = ddev->dev_private;
+	int i;
+
 	/* TODO: is this called for user defined modes? (xrandr --add-mode)
 	 * TODO: check that the mode fits in the framebuffer */
-	DRM_DEBUG("%s: %dx%d status=%d\n", mode->name, mode->hdisplay,
-		  mode->vdisplay, mode->status);
-	return MODE_OK;
+
+	if(qdev->monitors_config_width == mode->hdisplay &&
+	   qdev->monitors_config_height == mode->vdisplay)
+		return MODE_OK;
+
+	for (i = 0; i < ARRAY_SIZE(common_modes); i++) {
+		if (common_modes[i].w == mode->hdisplay && common_modes[i].h == mode->vdisplay)
+			return MODE_OK;
+	}
+	return MODE_BAD;
 }
 
 static struct drm_encoder *qxl_best_encoder(struct drm_connector *connector)
diff --git a/drivers/gpu/drm/qxl/qxl_drv.h b/drivers/gpu/drm/qxl/qxl_drv.h
index d8549690801d20..01a86948eb8cd6 100644
--- a/drivers/gpu/drm/qxl/qxl_drv.h
+++ b/drivers/gpu/drm/qxl/qxl_drv.h
@@ -325,6 +325,8 @@ struct qxl_device {
 	struct work_struct fb_work;
 
 	struct drm_property *hotplug_mode_update_property;
+	int monitors_config_width;
+	int monitors_config_height;
 };
 
 /* forward declaration for QXL_INFO_IO */