diff --git a/autoload/gitgutter/diff.vim b/autoload/gitgutter/diff.vim
index 710b611..24142a2 100644
--- a/autoload/gitgutter/diff.vim
+++ b/autoload/gitgutter/diff.vim
@@ -118,7 +118,7 @@ function! gitgutter#diff#handler(bufnr, diff) abort
   let modified_lines = s:process_hunks(a:bufnr, gitgutter#hunk#hunks(a:bufnr))
 
   if len(modified_lines) > g:gitgutter_max_signs
-    call gitgutter#utility#warn_once('exceeded maximum number of signs (configured by g:gitgutter_max_signs).', 'max_signs')
+    call gitgutter#utility#warn_once(a:bufnr, 'exceeded maximum number of signs (configured by g:gitgutter_max_signs).', 'max_signs')
     call gitgutter#sign#clear_signs(a:bufnr)
 
   else
diff --git a/autoload/gitgutter/utility.vim b/autoload/gitgutter/utility.vim
index abb6c37..29ea097 100644
--- a/autoload/gitgutter/utility.vim
+++ b/autoload/gitgutter/utility.vim
@@ -22,9 +22,9 @@ function! gitgutter#utility#warn(message) abort
   let v:warningmsg = a:message
 endfunction
 
-function! gitgutter#utility#warn_once(message, key) abort
-  if empty(gitgutter#utility#getbufvar(s:bufnr, a:key))
-    call gitgutter#utility#setbufvar(s:bufnr, a:key, '1')
+function! gitgutter#utility#warn_once(bufnr, message, key) abort
+  if empty(gitgutter#utility#getbufvar(a:bufnr, a:key))
+    call gitgutter#utility#setbufvar(a:bufnr, a:key, '1')
     echohl WarningMsg
     redraw | echo 'vim-gitgutter: ' . a:message
     echohl None