diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 938a839..831a894 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -2938,6 +2938,25 @@
   let g:bar = 123
   call extend(g:, #{bar: { -> "foo" }}, "keep")
   call assert_fails('call extend(g:, #{bar: { -> "foo" }}, "force")', 'E704:')
+  unlet g:bar
+
+  call assert_fails('call extend(l:, #{foo: { -> "foo" }})', 'E704:')
+  let bar = 123
+  call extend(l:, #{bar: { -> "foo" }}, "keep")
+  call assert_fails('call extend(l:, #{bar: { -> "foo" }}, "force")', 'E704:')
+  unlet bar
+
+  call assert_fails('call extend(g:, #{foo: function("extend")})', 'E704:')
+  let g:bar = 123
+  call extend(g:, #{bar: function("extend")}, "keep")
+  call assert_fails('call extend(g:, #{bar: function("extend")}, "force")', 'E704:')
+  unlet g:bar
+
+  call assert_fails('call extend(l:, #{foo: function("extend")})', 'E704:')
+  let bar = 123
+  call extend(l:, #{bar: function("extend")}, "keep")
+  call assert_fails('call extend(l:, #{bar: function("extend")}, "force")', 'E704:')
+  unlet bar
 endfunc
 
 func Test_funcref_to_string()