diff --git a/autoload/gitgutter/hunk.vim b/autoload/gitgutter/hunk.vim
index 9646d2e..349b7ca 100644
--- a/autoload/gitgutter/hunk.vim
+++ b/autoload/gitgutter/hunk.vim
@@ -466,7 +466,9 @@ function! s:open_hunk_preview_window()
     endif
   endif
 
-  let [previewpopup, &previewpopup] = [&previewpopup, '']
+  if exists('&previewpopup')
+    let [previewpopup, &previewpopup] = [&previewpopup, '']
+  endif
 
   " Specifying where to open the preview window can lead to the cursor going
   " to an unexpected window when the preview window is closed (#769).
@@ -487,7 +489,9 @@ function! s:open_hunk_preview_window()
     nnoremap <buffer> <silent> <Esc> :<C-U>wincmd p<Bar>pclose<CR>
   endif
 
-  let &previewpopup=previewpopup
+  if exists('&previewpopup')
+    let &previewpopup=previewpopup
+  endif
 endfunction