diff --git a/src/testdir/test_expr.vim b/src/testdir/test_expr.vim
index 7d7870e..f44e216 100644
--- a/src/testdir/test_expr.vim
+++ b/src/testdir/test_expr.vim
@@ -101,3 +101,8 @@
 func Test_set_reg_null_list()
   call setreg('x', test_null_list())
 endfunc
+
+func Test_special_char()
+  " The failure is only visible using valgrind.
+  call assert_fails('echo "\<C-">')
+endfunc