diff -up vim80/src/gui_gtk_x11.c.gtk3-render vim80/src/gui_gtk_x11.c

--- vim80/src/gui_gtk_x11.c.gtk3-render	2017-02-22 10:38:37.935193240 +0100

+++ vim80/src/gui_gtk_x11.c	2017-02-22 10:53:22.847435530 +0100

@@ -688,8 +688,13 @@ draw_event(GtkWidget *widget UNUSED,

 	    {

 		const cairo_rectangle_t rect = list->rectangles[i];

-		gui_mch_clear_block(Y_2_ROW(rect.y), 1,

-			Y_2_ROW(rect.y + rect.height - 1), Columns);

+		gui_mch_clear_block(Y_2_ROW((int)rect.y), 0,

+			Y_2_ROW((int)(rect.y + rect.height)) - 1, Columns - 1);

+           }

+

+           for (i = 0; i < list->num_rectangles; i++)

+           {

+               const cairo_rectangle_t rect = list->rectangles[i];

 		if (blink_mode)

 		    gui_gtk3_redraw(rect.x, rect.y, rect.width, rect.height);

@@ -6723,6 +6728,11 @@ gui_mch_clear_block(int row1, int col1,

     color.pixel = gui.back_pixel;

 #endif

+    col1 = check_col(col1);

+    col2 = check_col(col2);

+    row1 = check_row(row1);

+    row2 = check_row(row2);

+

 #if GTK_CHECK_VERSION(3,0,0)

     {

 	/* Add one pixel to the far right column in case a double-stroked