diff --git a/autoload/plug.vim b/autoload/plug.vim
index 7e52441..ac299a2 100644
--- a/autoload/plug.vim
+++ b/autoload/plug.vim
@@ -97,7 +97,7 @@ let s:plug_tab = get(s:, 'plug_tab', -1)
 let s:plug_buf = get(s:, 'plug_buf', -1)
 let s:mac_gui = has('gui_macvim') && has('gui_running')
 let s:is_win = has('win32') || has('win64')
-let s:nvim = has('nvim') && exists('*jobwait') && !s:is_win
+let s:nvim = has('nvim-0.2') || (has('nvim') && exists('*jobwait') && !s:is_win)
 let s:vim8 = has('patch-8.0.0039') && exists('*job_start')
 let s:me = resolve(expand('<sfile>:p'))
 let s:base_spec = { 'branch': 'master', 'frozen': 0 }
@@ -447,11 +447,15 @@ function! plug#load(...)
     let s = len(unknowns) > 1 ? 's' : ''
     return s:err(printf('Unknown plugin%s: %s', s, join(unknowns, ', ')))
   end
-  for name in a:000
-    call s:lod([name], ['ftdetect', 'after/ftdetect', 'plugin', 'after/plugin'])
-  endfor
-  call s:dobufread(a:000)
-  return 1
+  let unloaded = filter(copy(a:000), '!get(s:loaded, v:val, 0)')
+  if !empty(unloaded)
+    for name in unloaded
+      call s:lod([name], ['ftdetect', 'after/ftdetect', 'plugin', 'after/plugin'])
+    endfor
+    call s:dobufread(unloaded)
+    return 1
+  end
+  return 0
 endfunction
 
 function! s:remove_triggers(name)
@@ -575,7 +579,7 @@ function! s:infer_properties(name, repo)
       let uri = repo
     else
       if repo !~ '/'
-        let repo = 'vim-scripts/'. repo
+        throw printf('Invalid argument: %s (implicit `vim-scripts'' expansion is deprecated)', repo)
       endif
       let fmt = get(g:, 'plug_url_format', 'https://git::@github.com/%s.git')
       let uri = printf(fmt, repo)
@@ -1063,7 +1067,7 @@ function! s:update_finish()
       elseif has_key(spec, 'tag')
         let tag = spec.tag
         if tag =~ '\*'
-          let tags = s:lines(s:system('git tag --list '.string(tag).' --sort -version:refname 2>&1', spec.dir))
+          let tags = s:lines(s:system('git tag --list '.s:shellesc(tag).' --sort -version:refname 2>&1', spec.dir))
           if !v:shell_error && !empty(tags)
             let tag = tags[0]
             call s:log4(name, printf('Latest tag for %s -> %s', spec.tag, tag))
@@ -2022,7 +2026,7 @@ function! s:git_validate(spec, check_branch)
       " Check tag
       if has_key(a:spec, 'tag')
         let tag = s:system_chomp('git describe --exact-match --tags HEAD 2>&1', a:spec.dir)
-        if a:spec.tag !=# tag
+        if a:spec.tag !=# tag && a:spec.tag !~ '\*'
           let err = printf('Invalid tag: %s (expected: %s). Try PlugUpdate.',
                 \ (empty(tag) ? 'N/A' : tag), a:spec.tag)
         endif