diff -ura xfce4-panel-4.12.1/panel/panel-window.c xfce4-panel-4.12.1/panel/panel-window.c
--- xfce4-panel-4.12.1/panel/panel-window.c	2016-08-11 23:54:27.000000000 +0200
+++ xfce4-panel-4.12.1/panel/panel-window.c	2017-03-26 07:45:14.110558681 +0200
@@ -2106,8 +2106,8 @@
             {
               dest_y = MAX (a.y, b.y);
               dest_h = MIN (a.y + a.height, b.y + b.height) - dest_y;
-              if (dest_h > 0)
-                window->struts_edge = STRUTS_EDGE_NONE;
+              //if (dest_h > 0)
+                //window->struts_edge = STRUTS_EDGE_NONE;
             }
           else if ((window->struts_edge == STRUTS_EDGE_TOP && b.y < a.y)
                    || (window->struts_edge == STRUTS_EDGE_BOTTOM
@@ -2115,8 +2115,8 @@
             {
               dest_x = MAX (a.x, b.x);
               dest_w = MIN (a.x + a.width, b.x + b.width) - dest_x;
-              if (dest_w > 0)
-                window->struts_edge = STRUTS_EDGE_NONE;
+              //if (dest_w > 0)
+                //window->struts_edge = STRUTS_EDGE_NONE;
             }
         }
 
Only in package.new/xfce4-panel-4.12.1/panel: panel-window.c.rej