diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index 012a1af..59bf945 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -2836,6 +2836,7 @@
     int		after;	    /* where to add: 0 = before first one */
 {
     int		i;
+    int		old_argcount = ARGCOUNT;
 
     if (ga_grow(&ALIST(curwin)->al_ga, count) == OK)
     {
@@ -2852,8 +2853,8 @@
 	    ARGLIST[after + i].ae_fnum = buflist_add(files[i], BLN_LISTED);
 	}
 	ALIST(curwin)->al_ga.ga_len += count;
-	if (curwin->w_arg_idx >= after)
-	    ++curwin->w_arg_idx;
+	if (old_argcount > 0 && curwin->w_arg_idx >= after)
+	    curwin->w_arg_idx += count;
 	return after;
     }
 
diff --git a/src/testdir/test_arglist.vim b/src/testdir/test_arglist.vim
index 3f72f0f..5226317 100644
--- a/src/testdir/test_arglist.vim
+++ b/src/testdir/test_arglist.vim
@@ -20,3 +20,55 @@
   1argdelete
   call assert_equal(0, argidx())
 endfunc
+
+func Test_argadd()
+  %argdelete
+  argadd a b c
+  call assert_equal(0, argidx())
+
+  %argdelete
+  argadd a
+  call assert_equal(0, argidx())
+  argadd b c d
+  call assert_equal(0, argidx())
+
+  call Init_abc()
+  argadd x
+  call Assert_argc(['a', 'b', 'x', 'c'])
+  call assert_equal(1, argidx())
+
+  call Init_abc()
+  0argadd x
+  call Assert_argc(['x', 'a', 'b', 'c'])
+  call assert_equal(2, argidx())
+
+  call Init_abc()
+  1argadd x
+  call Assert_argc(['a', 'x', 'b', 'c'])
+  call assert_equal(2, argidx())
+
+  call Init_abc()
+  $argadd x
+  call Assert_argc(['a', 'b', 'c', 'x'])
+  call assert_equal(1, argidx())
+
+  call Init_abc()
+  $argadd x
+  +2argadd y
+  call Assert_argc(['a', 'b', 'c', 'x', 'y'])
+  call assert_equal(1, argidx())
+endfunc
+
+func Init_abc()
+  args a b c
+  next
+endfunc
+
+func Assert_argc(l)
+  call assert_equal(len(a:l), argc())
+  let i = 0
+  while i < len(a:l) && i < argc()
+    call assert_equal(a:l[i], argv(i))
+    let i += 1
+  endwhile
+endfunc
diff --git a/src/version.c b/src/version.c
index 76e176a..09176eb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1123,
+/**/
     1122,
 /**/
     1121,