diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index 8160af3..53f5a2e 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -192,6 +192,7 @@
   if cmd !~ '-u NONE'
     let cmd = cmd . ' -u NONE'
   endif
+  let cmd .= ' --not-a-term'
 
   " With pipecmd we can't set VIMRUNTIME.
   if a:pipecmd != ''