diff --git a/doc/lualine.txt b/doc/lualine.txt
index 0bcfe5e..b1a26e5 100644
--- a/doc/lualine.txt
+++ b/doc/lualine.txt
@@ -465,6 +465,11 @@ General component options              These are options that control behavior
                        --   padding = { left = left_padding, right = right_padding }
     
           fmt = nil,   -- Format function, formats the component's output.
+                       -- This function receives two arguments:
+                       -- - string that is going to be displayed and
+                       --   that can be changed, enhanced and etc.
+                       -- - context object with information you might
+                       --   need. E.g. tabnr if used with tabs.
           on_click = nil, -- takes a function that is called when component is clicked with mouse.
                        -- the function receives several arguments
                        -- - number of clicks incase of multiple clicks
@@ -673,6 +678,16 @@ Component specific options             These are options that are available on
             active = 'lualine_{section}_normal',     -- Color for active tab.
             inactive = 'lualine_{section}_inactive', -- Color for inactive tab.
           },
+    
+          fmt = function(name, context)
+            -- Show + if buffer is modified in tab
+            local buflist = vim.fn.tabpagebuflist(context.tabnr)
+            local winnr = vim.fn.tabpagewinnr(context.tabnr)
+            local bufnr = buflist[winnr]
+            local mod = vim.fn.getbufvar(bufnr, '&mod')
+    
+            return name .. (mod == 1 and ' +' or '')
+          end
         }
       }
     }