diff --git a/src/testdir/test_window_cmd.vim b/src/testdir/test_window_cmd.vim
index e042160..19b4466 100644
--- a/src/testdir/test_window_cmd.vim
+++ b/src/testdir/test_window_cmd.vim
@@ -1424,6 +1424,12 @@
     call assert_true(id->win_move_separator(-offset))
     call assert_equal(w, winwidth(id))
   endfor
+  " check win_move_separator from right window on right window is no-op
+  let w0 = winwidth(0)
+  call assert_true(win_move_separator(0, 1))
+  call assert_equal(w0, winwidth(0))
+  call assert_true(win_move_separator(0, -1))
+  call assert_equal(w0, winwidth(0))
   " check that win_move_separator doesn't error with offsets beyond moving
   " possibility
   call assert_true(win_move_separator(id, 5000))
@@ -1465,6 +1471,19 @@
     call assert_true(win_move_statusline(1, -offset))
     call assert_equal(h, winheight(1))
   endfor
+  " check win_move_statusline from bottom window on bottom window
+  let h0 = winheight(0)
+  for offset in range(5)
+    call assert_true(0->win_move_statusline(-offset))
+    call assert_equal(h0 - offset, winheight(0))
+    call assert_equal(1 + offset, &cmdheight)
+    call assert_true(win_move_statusline(0, offset))
+    call assert_equal(h0, winheight(0))
+    call assert_equal(1, &cmdheight)
+  endfor
+  call assert_true(win_move_statusline(0, 1))
+  call assert_equal(h0, winheight(0))
+  call assert_equal(1, &cmdheight)
   " check win_move_statusline from bottom window on top window ID
   let id = win_getid(1)
   for offset in range(5)
diff --git a/src/version.c b/src/version.c
index 005a394..13de4a4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4248,
+/**/
     4247,
 /**/
     4246,
diff --git a/src/window.c b/src/window.c
index c77149f..f80334d 100644
--- a/src/window.c
+++ b/src/window.c
@@ -6187,7 +6187,9 @@
     if (offset <= 0)		// No room at all, quit.
 	return;
     if (fr == NULL)
-	return;			// Safety check, should not happen.
+	// This can happen when calling win_move_separator() on the rightmost
+	// window.  Just don't do anything.
+	return;			
 
     // grow frame fr by offset lines
     frame_new_width(fr, fr->fr_width + offset, left, FALSE);