diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index a2490be355..cccf1e50ff 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -2994,7 +2994,6 @@ char_u *get_user_var_name(expand_T *xp, int idx)
   static size_t tdone;
   static size_t vidx;
   static hashitem_T   *hi;
-  hashtab_T           *ht;
 
   if (idx == 0) {
     gdone = bdone = wdone = vidx = 0;
@@ -3015,7 +3014,10 @@ char_u *get_user_var_name(expand_T *xp, int idx)
   }
 
   // b: variables
-  ht = &curbuf->b_vars->dv_hashtab;
+  // In cmdwin, the alternative buffer should be used.
+  hashtab_T *ht = (cmdwin_type != 0 && get_cmdline_type() == NUL)
+    ? &prevwin->w_buffer->b_vars->dv_hashtab
+    : &curbuf->b_vars->dv_hashtab;
   if (bdone < ht->ht_used) {
     if (bdone++ == 0)
       hi = ht->ht_array;
@@ -3027,7 +3029,10 @@ char_u *get_user_var_name(expand_T *xp, int idx)
   }
 
   // w: variables
-  ht = &curwin->w_vars->dv_hashtab;
+  // In cmdwin, the alternative window should be used.
+  ht = (cmdwin_type != 0 && get_cmdline_type() == NUL)
+    ? &prevwin->w_vars->dv_hashtab
+    : &curwin->w_vars->dv_hashtab;
   if (wdone < ht->ht_used) {
     if (wdone++ == 0)
       hi = ht->ht_array;
diff --git a/src/nvim/testdir/test_ins_complete.vim b/src/nvim/testdir/test_ins_complete.vim
index 1339a9f25d..b8632b9595 100644
--- a/src/nvim/testdir/test_ins_complete.vim
+++ b/src/nvim/testdir/test_ins_complete.vim
@@ -327,7 +327,10 @@ func Test_compl_in_cmdwin()
   set wildmenu wildchar=<Tab>
   com! -nargs=1 -complete=command GetInput let input = <q-args>
   com! -buffer TestCommand echo 'TestCommand'
+  let w:test_winvar = 'winvar'
+  let b:test_bufvar = 'bufvar'
 
+  " User-defined commands
   let input = ''
   call feedkeys("q:iGetInput T\<C-x>\<C-v>\<CR>", 'tx!')
   call assert_equal('TestCommand', input)
@@ -336,8 +339,29 @@ func Test_compl_in_cmdwin()
   call feedkeys("q::GetInput T\<Tab>\<CR>:q\<CR>", 'tx!')
   call assert_equal('T', input)
 
+  com! -nargs=1 -complete=var GetInput let input = <q-args>
+  " Window-local variables
+  let input = ''
+  call feedkeys("q:iGetInput w:test_\<C-x>\<C-v>\<CR>", 'tx!')
+  call assert_equal('w:test_winvar', input)
+
+  let input = ''
+  call feedkeys("q::GetInput w:test_\<Tab>\<CR>:q\<CR>", 'tx!')
+  call assert_equal('w:test_', input)
+
+  " Buffer-local variables
+  let input = ''
+  call feedkeys("q:iGetInput b:test_\<C-x>\<C-v>\<CR>", 'tx!')
+  call assert_equal('b:test_bufvar', input)
+
+  let input = ''
+  call feedkeys("q::GetInput b:test_\<Tab>\<CR>:q\<CR>", 'tx!')
+  call assert_equal('b:test_', input)
+
   delcom TestCommand
   delcom GetInput
+  unlet w:test_winvar
+  unlet b:test_bufvar
   set wildmenu& wildchar&
 endfunc