diff --git a/autoload/go/fmt.vim b/autoload/go/fmt.vim
index 380034f136..cd1245607d 100644
--- a/autoload/go/fmt.vim
+++ b/autoload/go/fmt.vim
@@ -58,7 +58,7 @@ function! go#fmt#Format(withGoimport) abort
   endif
 
   " Write current unsaved buffer to a temp file
-  let l:tmpname = tempname()
+  let l:tmpname = tempname() . '.go'
   call writefile(go#util#GetLines(), l:tmpname)
   if go#util#IsWin()
     let l:tmpname = tr(l:tmpname, '\', '/')