diff --git a/autoload/airline/extensions/hunks.vim b/autoload/airline/extensions/hunks.vim
index 88499fa..2a89f78 100644
--- a/autoload/airline/extensions/hunks.vim
+++ b/autoload/airline/extensions/hunks.vim
@@ -1,13 +1,21 @@
 " MIT License. Copyright (c) 2013 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
+function! s:check_defined(variable, default)
+  if !exists(a:variable)
+    let {a:variable} = a:default
+  endif
+endfunction
+
+call s:check_defined('g:airline#extensions#hunks#non_zero_only', 0)
+call s:check_defined('g:airline#extensions#hunks#hunk_symbols', ['+', '~', '-'])
+
 function! airline#extensions#hunks#get_hunks()
   let hunks = GitGutterGetHunkSummary()
-  let hunk_symbol = ['+', '~', '-']
   let string = ''
   for i in [0, 1, 2]
-    if g:airline_hunk_non_zero_only == 0 || hunks[i] > 0
-      let string .= printf('%s%s ', hunk_symbol[i], hunks[i])
+    if g:airline#extensions#hunks#non_zero_only == 0 || hunks[i] > 0
+      let string .= printf('%s%s ', g:airline#extensions#hunks#hunk_symbols[i], hunks[i])
     endif
   endfor
   return string
diff --git a/doc/airline.txt b/doc/airline.txt
index 44da7f7..139a237 100644
--- a/doc/airline.txt
+++ b/doc/airline.txt
@@ -211,9 +211,13 @@ vim-gitgutter <https://github.com/airblade/vim-gitgutter>
 
 * enable/disable detecting changed hunks under source control. >
   let g:airline_enable_hunks = 1
-
-* enable/disable showing only non-zero hunks.
-  let g:airline_hunk_non_zero_only = 0
+<
+* enable/disable showing only non-zero hunks. >
+  let g:airline#extensions#hunks#non_zero_only = 0
+<
+* set hunk count symbols. >
+  let g:airline#extensions#hunks#hunk_symbols = ['+', '~', '-']
+<
 
 ==============================================================================
 FUNCREFS                                                  *airline-funcrefs*
diff --git a/plugin/airline.vim b/plugin/airline.vim
index a2990bc..b47653a 100644
--- a/plugin/airline.vim
+++ b/plugin/airline.vim
@@ -25,7 +25,6 @@ call s:check_defined('g:airline_detect_iminsert', 0)
 call s:check_defined('g:airline_detect_modified', 1)
 call s:check_defined('g:airline_detect_paste', 1)
 call s:check_defined('g:airline_detect_whitespace', 1)
-call s:check_defined('g:airline_hunk_non_zero_only', 0)
 call s:check_defined('g:airline_branch_empty_message', '')
 call s:check_defined('g:airline_branch_prefix', exists('g:airline_powerline_fonts')?' ':'')
 call s:check_defined('g:airline_readonly_symbol', exists('g:airline_powerline_fonts')?'':'RO')