diff --git a/src/testdir/test_expr.vim b/src/testdir/test_expr.vim
index 40c1701..5f2020d 100644
--- a/src/testdir/test_expr.vim
+++ b/src/testdir/test_expr.vim
@@ -157,12 +157,28 @@
 
 func Test_loop_over_null_list()
   let lines =<< trim END
-      VAR null_list = test_null_list()
-      for i in null_list
+      VAR nulllist = test_null_list()
+      for i in nulllist
         call assert_report('should not get here')
       endfor
   END
   call v9.CheckLegacyAndVim9Success(lines)
+
+  let lines =<< trim END
+      var nulllist = null_list
+      for i in nulllist
+        call assert_report('should not get here')
+      endfor
+  END
+  call v9.CheckDefAndScriptSuccess(lines)
+
+  let lines =<< trim END
+      let nulllist = null_list
+      for i in nulllist
+        call assert_report('should not get here')
+      endfor
+  END
+  call v9.CheckScriptFailure(lines, 'E121: Undefined variable: null_list')
 endfunc
 
 func Test_setreg_null_list()