diff --git a/src/testdir/test_expr.vim b/src/testdir/test_expr.vim
index 2cd9625..142455b 100644
--- a/src/testdir/test_expr.vim
+++ b/src/testdir/test_expr.vim
@@ -85,7 +85,7 @@
 endfunc
 
 func Test_loop_over_null_list()
-  let null_list = submatch(1, 1)
+  let null_list = test_null_list()
   for i in null_list
     call assert_true(0, 'should not get here')
   endfor