diff --git a/autoload/gitmessenger/blame.vim b/autoload/gitmessenger/blame.vim
index d42e7bc..423ee6c 100644
--- a/autoload/gitmessenger/blame.vim
+++ b/autoload/gitmessenger/blame.vim
@@ -442,7 +442,7 @@ function! s:blame__after_blame(git) dict abort
 endfunction
 
 function! s:blame__spawn_git(args, callback) dict abort
-    let git = gitmessenger#git#new(g:git_messenger_git_command, self.git_root)
+    let git = gitmessenger#git#new(g:git_messenger_git_command, self.gitdir, self.worktree)
     let CB = a:callback
     if type(CB) == v:t_string
         let CB = funcref(CB, [], self)
@@ -465,7 +465,8 @@ let s:blame.start = funcref('s:blame__start')
 " interface Blame {
 "   state: BlameHistory;
 "   line: number;
-"   git_root: string;
+"   gitdir: string;
+"   worktree: string;
 "   blame_file: string;
 "   prev_commit?: string;
 "   oldest_commit?: string;
@@ -490,10 +491,12 @@ function! gitmessenger#blame#new(file, line, opts) abort
     let b.opts = a:opts
 
     let dir = fnamemodify(file, ':p:h')
-    let b.git_root = gitmessenger#git#root_dir(dir)
+    let gitdir = gitmessenger#git#gitdir(dir)
+    let b.gitdir = gitdir !=# '' ? gitdir : $GIT_DIR
+    let b.worktree = $GIT_WORK_TREE !=# '' ? fnamemodify($GIT_WORK_TREE, ':p') : fnamemodify(gitdir, ':h')
 
     " Validations
-    if b.git_root ==# ''
+    if b.gitdir ==# ''
         call b.error("git-messenger: Directory '" . dir . "' is not inside a Git repository")
         return v:null
     endif
diff --git a/autoload/gitmessenger/git.vim b/autoload/gitmessenger/git.vim
index b79ad9f..6cc465e 100644
--- a/autoload/gitmessenger/git.vim
+++ b/autoload/gitmessenger/git.vim
@@ -1,6 +1,6 @@
 let s:SEP = has('win32') ? '\' : '/'
 
-function! s:find_dotgit(from) abort
+function! s:find_gitdir(from) abort
     let dir = finddir('.git', a:from . ';')
     let file = findfile('.git', a:from . ';')
 
@@ -22,21 +22,21 @@ function! s:find_dotgit(from) abort
     " chosen.
     " When `dir` or `file` is empty, the other is chosen so we don't need to
     " care about empty string here.
-    let dotgit = len(dir) > len(file) ? dir : file
+    let gitdir = len(dir) > len(file) ? dir : file
 
     " Inside .git directory is outside repository
     " This check must be done before chopping last path separator otherwise it
     " matches to directory like /path/to/.github/ (#70)
-    if stridx(a:from, dotgit) == 0
+    if stridx(a:from, gitdir) == 0
         return ''
     endif
 
-    if dotgit[-1:] ==# s:SEP
+    if gitdir[-1:] ==# s:SEP
         " [:-2] chops last path separator (/path/to/.git/ => /path/to/.git)
-        let dotgit = dotgit[:-2]
+        let gitdir = gitdir[:-2]
     endif
 
-    return dotgit
+    return gitdir
 endfunction
 
 " Params:
@@ -44,20 +44,16 @@ endfunction
 "     base path to find .git in ancestor directories
 " Returns:
 "   string
-"     empty string means root directory was not found
-function! gitmessenger#git#root_dir(from) abort
+"     empty string means git dir was not found
+function! gitmessenger#git#gitdir(from) abort
     let from = fnameescape(fnamemodify(a:from, ':p'))
     if from[-1:] ==# s:SEP
         " [:-2] chops last path separator
         let from = from[:-2]
     endif
-    let dotgit = s:find_dotgit(from)
-    if dotgit ==# ''
-        return ''
-    endif
+    let gitdir = s:find_gitdir(from)
 
-    " /path/to/.git => /path/to
-    return fnamemodify(dotgit, ':h')
+    return gitdir
 endfunction
 
 let s:git = {}
@@ -124,12 +120,12 @@ endif
 " Returns:
 "   Job ID of the spawned process
 function! s:git__spawn(args, on_exit) dict abort
-    let cmdline = [self.cmd, '-C', self.dir] + a:args
+    let cmdline = [self.cmd, '--git-dir', self.gitdir, '--work-tree', self.worktree] + a:args
     if has('nvim')
         let self.stdout = ['']
         let self.stderr = ['']
         let job_id = jobstart(cmdline, {
-                    \   'cwd': self.dir,
+                    \   'cwd': self.worktree,
                     \   'on_stdout' : funcref('s:on_output_nvim', [], self),
                     \   'on_stderr' : funcref('s:on_output_nvim', [], self),
                     \   'on_exit' : funcref('s:on_exit_nvim', [], self),
@@ -143,7 +139,7 @@ function! s:git__spawn(args, on_exit) dict abort
         let self.stdout = []
         let self.stderr = []
         let job_id = job_start(cmdline, {
-                    \   'cwd': self.dir,
+                    \   'cwd': self.worktree,
                     \   'out_cb' : funcref('s:on_output_vim', ['stdout'], self),
                     \   'err_cb' : funcref('s:on_output_vim', ['stderr'], self),
                     \   'exit_cb' : funcref('s:on_exit_vim', [], self),
@@ -166,9 +162,10 @@ let s:git.spawn = funcref('s:git__spawn')
 "     Directory path to run Git
 " Returns:
 "   Git object
-function! gitmessenger#git#new(cmd, dir) abort
+function! gitmessenger#git#new(cmd, gitdir, worktree) abort
     let g = deepcopy(s:git)
     let g.cmd = a:cmd
-    let g.dir = a:dir
+    let g.gitdir = a:gitdir
+    let g.worktree = a:worktree
     return g
 endfunction
diff --git a/test/all.vimspec b/test/all.vimspec
index 426e9c2..b4fcad8 100644
--- a/test/all.vimspec
+++ b/test/all.vimspec
@@ -1290,7 +1290,7 @@ Describe git-messenger.vim
         End
     End
 
-    Describe gitmessenger#git#root_dir()
+    Describe gitmessenger#git#gitdir()
         Before all
             let root_dir = './my git root with space'
             let file = 'file.txt'
@@ -1314,12 +1314,12 @@ Describe git-messenger.vim
             " call fnamemodify here the same way
             " gitmessenger#blame#new() does to get our absolute path
             let file = './my git root with space/file.txt'
-            let expected_root_dir = fnamemodify(file, ':p:h')
-            let actual_root_dir = gitmessenger#git#root_dir(file)
+            let expected_gitdir = fnamemodify(file, ':p:h') .. '/.git'
+            let actual_gitdir = gitmessenger#git#gitdir(file)
 
             " Failure will return the repo root instead of our created
             " ad-hoc root directory
-            Assert Equal(actual_root_dir, expected_root_dir)
+            Assert Equal(actual_gitdir, expected_gitdir)
         End
     End
 
@@ -1441,8 +1441,8 @@ Describe git-messenger.vim
     End
 
     Describe gitmessenger#git#new
-        It runs Git command at specified directory using -C
-            let git = gitmessenger#git#new('echo', '.')
+        It runs Git command at specified directory using --git-dir and --work-tree
+            let git = gitmessenger#git#new('echo', '.', '.')
             let state = {}
             let OnExit = {g -> extend(state, {'exit': g.exit_status})}
 
@@ -1451,11 +1451,11 @@ Describe git-messenger.vim
 
             Assert True(len(git.stdout) > 0, string(git.stdout))
             let stdout = git.stdout[0]
-            Assert True(stridx(stdout, '-C .') >= 0, string(stdout))
+            Assert True(stridx(stdout, '--git-dir . --work-tree .') >= 0, string(stdout))
         End
 
         It trims trailing \r (#75)
-            let git = gitmessenger#git#new('echo', '.')
+            let git = gitmessenger#git#new('echo', '.', '.')
             let state = {}
             let OnExit = {g -> extend(state, {'exit': g.exit_status})}