diff --git a/README.md b/README.md
index 3b21fd2..bfae2e1 100644
--- a/README.md
+++ b/README.md
@@ -391,18 +391,14 @@ set statusline=%!v:lua.statusline()
 " Also works in expression mappings
 lua << EOF
 function _G.check_back_space()
-    local col = vim.fn.col('.') - 1
-    if col == 0 or vim.fn.getline('.'):sub(col, col):match('%s') then
-        return true
-    else
-        return false
-    end
+    local col = vim.api.nvim_win_get_cursor(0)[2]
+    return (col == 0 or vim.api.nvim_get_current_line():sub(col, col):match('%s')) and true
 end
 EOF
 
 inoremap <silent> <expr> <Tab>
-    \ pumvisible() ? '\<C-n>' :
-    \ v:lua.check_back_space() ? '\<Tab>' :
+    \ pumvisible() ? "\<C-n>" :
+    \ v:lua.check_back_space() ? "\<Tab>" :
     \ completion#trigger_completion()
 ```
 
diff --git a/doc/nvim-lua-guide.txt b/doc/nvim-lua-guide.txt
index e21c77f..3c8db4d 100644
--- a/doc/nvim-lua-guide.txt
+++ b/doc/nvim-lua-guide.txt
@@ -414,18 +414,15 @@ types and vice versa.
     " Also works in expression mappings
     lua << EOF
     function _G.check_back_space()
-        local col = vim.fn.col('.') - 1
-        if col == 0 or vim.fn.getline('.'):sub(col, col):match('%s') then
-            return true
-        else
-            return false
-        end
+        local col = vim.api.nvim_win_get_cursor(0)[2]
+        return (col == 0 or vim.api.nvim_get_current_line():sub(col,
+        col):match('%s')) and true
     end
     EOF
 
     inoremap <silent> <expr> <Tab>
-        \ pumvisible() ? '\<C-n>' :
-        \ v:lua.check_back_space() ? '\<Tab>' :
+        \ pumvisible() ? "\<C-n>" :
+        \ v:lua.check_back_space() ? "\<Tab>" :
         \ completion#trigger_completion()
 <