diff --git a/README.md b/README.md
index 484edba..3e1f852 100644
--- a/README.md
+++ b/README.md
@@ -178,10 +178,17 @@ mapping = {
 You can specify your own custom mapping function.
 
 ```lua
+local check_back_space = function()
+    local col = vim.fn.col('.') - 1
+    return col == 0 or vim.fn.getline('.'):sub(col, col):match('%s')
+end
+
 mapping = {
   ['<Tab>'] = function(fallback)
     if vim.fn.pumvisible() == 1 then
       vim.fn.feedkeys(vim.api.nvim_replace_termcodes('<C-n>', true, true, true), 'n')
+    elseif check_back_space() then
+      vim.fn.feedkeys(vim.api.nvim_replace_termcodes('<Tab>', true, true, true), 'n')
     elseif vim.fn['vsnip#available']() == 1 then
       vim.fn.feedkeys(vim.api.nvim_replace_termcodes('<Plug>(vsnip-expand-or-jump)', true, true, true), '')
     else