diff --git a/autoload/gitgutter/diff.vim b/autoload/gitgutter/diff.vim
index 9441f7a..b284132 100644
--- a/autoload/gitgutter/diff.vim
+++ b/autoload/gitgutter/diff.vim
@@ -100,7 +100,7 @@ function! gitgutter#diff#run_diff(bufnr, preserve_full_diff) abort
   call s:write_buffer(a:bufnr, buff_file)
 
   " Call git-diff with the temporary files.
-  let cmd .= g:gitgutter_git_executable.' --no-pager'
+  let cmd .= g:gitgutter_git_executable.' --git-dir="" --no-pager'
   if s:c_flag
     let cmd .= ' -c "diff.autorefreshindex=0"'
     let cmd .= ' -c "diff.noprefix=false"'