diff --git a/plugin/fugitive.vim b/plugin/fugitive.vim
index 8c02768..67f1ab7 100644
--- a/plugin/fugitive.vim
+++ b/plugin/fugitive.vim
@@ -558,7 +558,7 @@ function! s:Diff(...) abort
       let file = s:buffer().expand(a:1)
     endif
     if file !~ ':' && file !~ '^/'
-      let file = file.s:buffer.path(':')
+      let file = file.s:buffer().path(':')
     endif
   else
     let file = s:buffer().path(s:buffer().commit() == '' ? ':' : '/')