diff --git a/autoload/ag.vim b/autoload/ag.vim
index 432ef444..9b9401ee 100644
--- a/autoload/ag.vim
+++ b/autoload/ag.vim
@@ -57,7 +57,7 @@ if !exists("g:ag_mapping_message")
 endif
 
 if !exists("g:ag_working_path_mode")
-    let g:ag_working_path_mode = 'c'
+  let g:ag_working_path_mode = 'c'
 endif
 
 function! ag#AgBuffer(cmd, args)
@@ -114,17 +114,18 @@ function! ag#Ag(cmd, args)
     set t_te=
     if g:ag_working_path_mode ==? 'r' " Try to find the projectroot for current buffer
       let l:cwd_back = getcwd()
-      let l:cwd = s:guessProjectRoot()
+      let l:cwd = g:Ag_get_project_root()
       try
-        exe "lcd ".l:cwd
+        exe "lcd" l:cwd
+        echo 'Searching from' l:cwd
       catch
-        echom 'Failed to change directory to:'.l:cwd
+        echom 'Failed to change directory to' l:cwd
       finally
-        silent! execute a:cmd . " " . escape(l:grepargs, '|')
+        silent! execute a:cmd escape(l:grepargs, '|')
         exe "lcd ".l:cwd_back
       endtry
     else " Someone chose an undefined value or 'c' so we revert to the default
-      silent! execute a:cmd . " " . escape(l:grepargs, '|')
+      silent! execute a:cmd escape(l:grepargs, '|')
     endif
   finally
     let &grepprg=l:grepprg_bak
@@ -232,3 +233,9 @@ function! s:guessProjectRoot()
   " Nothing found, fallback to current working dir
   return getcwd()
 endfunction
+
+if !exists("g:Ag_get_project_root")
+  let g:Ag_get_project_root = function("s:guessProjectRoot")
+endif
+
+" vim:ts=2:sw=2:et
diff --git a/doc/ag.txt b/doc/ag.txt
index e702c291..1da13a0c 100644
--- a/doc/ag.txt
+++ b/doc/ag.txt
@@ -94,9 +94,11 @@ For background, see: https://github.com/rking/ag.vim/pull/88
                                                        *g:ag_working_path_mode*
 A mapping that describes where ag will be run. Default is the current working
 directory. Specifying 'r' as the argument will tell it to run from the project
-rootdirectory. For now any other mapping will result to the default.
-Example:
+rootdirectory. For now any other mapping will result to the default. The
+function that locates the root directory can be customized with
+|g:Ag_get_project_root|. Example: >
   let g:ag_working_path_mode='r'
+<
 
                                                                *g:ag_highlight*
 If 1, highlight the search terms after searching. Default: 0. Example: >
@@ -146,6 +148,13 @@ the mappings are not applied (see |g:ag_apply_qmappings| and
   let g:ag_mapping_message=0
 <
 
+                                                         *g:Ag_get_project_root*
+An alternative function to use when searching for the project root when
+|g:ag_working_path_mode| is set to 'r'. It should return the root directory
+from which ag will be executed. Example: >
+  let g:Ag_get_project_root=function("s:guessProjectRoot")
+<
+
 ==============================================================================
 MAPPINGS                                                         *ag-mappings*