diff --git a/lisp/frame.el b/lisp/frame.el
index cec2624..8dad63f 100644
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -123,8 +123,6 @@ handle-delete-frame
             ;; not a child frame.
             (when (and (not (eq frame-1 frame))
                        (frame-visible-p frame-1)
-                       (window-live-p (minibuffer-window frame-1))
-                       (eq (window-frame (minibuffer-window frame-1)) frame-1)
                        (not (frame-parent frame-1))
                        (not (frame-parameter frame-1 'delete-before)))
               (throw 'other-frame t))))
diff --git a/src/frame.c b/src/frame.c
index 681a245..b108e45 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -1560,15 +1560,16 @@ of them (the selected terminal frame) is actually displayed.
  * Return true if there exists at least one visible or iconified frame
  * but F.  Return false otherwise.
  *
- * Always return false when all remaining frames are either tooltip or
- * child frames or frames with a non-nil `delete-before' parameter.  If
- * INVISIBLE is false, also return false when the minibuffer window of
- * all remaining frames is on F.
-
+ * INVISIBLE true means we are called from make_frame_invisible where
+ * such a frame must be visible or iconified.  INVISIBLE nil means we
+ * are called from delete_frame.  In that case FORCE true means that the
+ * visibility status of such a frame can be ignored.
+ *
  * If F is the terminal frame and we are using X, return true if at
- * least one X frame exists.  */
+ * least one X frame exists.
+ */
 static bool
-other_frames (struct frame *f, bool invisible)
+other_frames (struct frame *f, bool invisible, bool force)
 {
   Lisp_Object frames, frame, frame1;
   struct frame *f1;
@@ -1591,23 +1592,20 @@ of them (the selected terminal frame) is actually displayed.
 	    x_sync (f1);
 #endif
 	  if (NILP (Fframe_parameter (frame1, Qtooltip))
-	      /* Tooltips and child frames don't count.  */
+	      /* Tooltips and child frames count neither for
+		 invisibility nor for deletions.  */
 	      && !FRAME_PARENT_FRAME (f1)
 	      /* Frames with a non-nil `delete-before' parameter don't
-		 count - either they depend on us or they depend on a
-		 frame that we will have to find right here.  */
-	      && NILP (get_frame_param (f1, Qdelete_before))
-	      /* Frames whose minibuffer window is on F don't count
-		 unless INVISIBLE is set - in that case F is either made
-		 invisible and may be autoraised from such a frame or
-		 the FORCE argument of delete_frame was non-nil.  */
-	      && (invisible || NILP (minibuffer_window)
-		  || !EQ (FRAME_MINIBUF_WINDOW (f1), minibuffer_window))
-	      /* At least one visible/iconified frame must remain.  */
+		 count for deletions.  */
+	      && (invisible || NILP (get_frame_param (f1, Qdelete_before)))
+	      /* For invisibility and normal deletions, at least one
+		 visible or iconified frame must remain (Bug#26682).  */
 	      && (FRAME_VISIBLE_P (f1) || FRAME_ICONIFIED_P (f1)
-		  /* Allow deleting the terminal frame when at least one
-		     X frame exists.  */
-		  || (FRAME_WINDOW_P (f1) && !FRAME_WINDOW_P (f))))
+		  || (!invisible
+		      && (force
+			  /* Allow deleting the terminal frame when at
+			     least one X frame exists.  */
+			  || (FRAME_WINDOW_P (f1) && !FRAME_WINDOW_P (f))))))
 	    return true;
 	}
     }
@@ -1680,7 +1678,7 @@ of them (the selected terminal frame) is actually displayed.

   if (!FRAME_LIVE_P (f))
     return Qnil;
-  else if (!EQ (force, Qnoelisp) && !other_frames (f, !NILP (force)))
+  else if (!EQ (force, Qnoelisp) && !other_frames (f, false, true))
     {
       if (NILP (force))
 	error ("Attempt to delete the sole visible or iconified frame");
@@ -1752,7 +1750,7 @@ of them (the selected terminal frame) is actually displayed.
      one.  */
   if (!FRAME_LIVE_P (f))
     return Qnil;
-  else if (!EQ (force, Qnoelisp) && !other_frames (f, !NILP (force)))
+  else if (!EQ (force, Qnoelisp) && !other_frames (f, false, true))
     {
       if (NILP (force))
 	error ("Attempt to delete the sole visible or iconified frame");
@@ -2275,7 +2273,7 @@ of them (the selected terminal frame) is actually displayed.
 {
   struct frame *f = decode_live_frame (frame);

-  if (NILP (force) && !other_frames (f, true))
+  if (NILP (force) && !other_frames (f, true, false))
     error ("Attempt to make invisible the sole visible or iconified frame");

   /* Don't allow minibuf_window to remain on an invisible frame.  */
@@ -2878,6 +2876,9 @@ Each element of ALIST has the form (PARM . VALUE), where PARM is a symbol.
   struct frame *f = decode_live_frame (frame);
   Lisp_Object prop, val;

+  if (EQ (alist, Qt))
+    return Qnil;
+
   /* I think this should be done with a hook.  */
 #ifdef HAVE_WINDOW_SYSTEM
   if (FRAME_WINDOW_P (f))