diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index 223a6e4..c91cd65 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -639,6 +639,23 @@
       extend(test_null_list(), ['x'])
   END
   CheckScriptFailure(lines, 'E1134:', 2)
+
+  # using global var has no declared type
+  g:myList = []
+  g:myList->extend([1])
+  g:myList->extend(['x'])
+  assert_equal([1, 'x'], g:myList)
+  unlet g:myList
+
+  # using declared list gives an error
+  lines =<< trim END
+      var l: list<number>
+      g:myList = l
+      g:myList->extend([1])
+      g:myList->extend(['x'])
+  END
+  CheckDefExecAndScriptFailure(lines, 'E1013: Argument 2: type mismatch, expected list<number> but got list<string>', 4)
+  unlet g:myList
 enddef
 
 def Test_extend_dict()
@@ -963,6 +980,23 @@
   var anyDict: dict<any> = {a: 0}
   assert_equal({a: 0, b: 'x'}, extend(anyDict, {b: 'x'}))
 
+  # using global var, which has no declared type
+  g:myDict = {}
+  g:myDict->extend({a: 1})
+  g:myDict->extend({b: 'x'})
+  assert_equal({a: 1, b: 'x'}, g:myDict)
+  unlet g:myDict
+
+  # using list with declared type gives an error
+  lines =<< trim END
+      var d: dict<number>
+      g:myDict = d
+      g:myDict->extend({a: 1})
+      g:myDict->extend({b: 'x'})
+  END
+  CheckDefExecAndScriptFailure(lines, 'E1013: Argument 2: type mismatch, expected dict<number> but got dict<string>', 4)
+  unlet g:myDict
+
   # assignment to script-local dict
   lines =<< trim END
     vim9script
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index 7b83510..d957c15 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -982,26 +982,22 @@
   END
   CheckDefAndScriptSuccess(lines)
 
-  # FIXME: this should not fail when compiled
   lines =<< trim END
-      vim9script
       assert_equal([1, 2, "x"], extend([1, 2], ["x"]))
       assert_equal([1, "b", 1], extend([1], ["b", 1]))
+
+      assert_equal({a: 1, b: "x"}, extend({a: 1}, {b: "x"}))
   END
-  CheckScriptSuccess(lines)
+  CheckDefAndScriptSuccess(lines)
 
   CheckDefAndScriptFailure(['extend("a", 1)'], ['E1013: Argument 1: type mismatch, expected list<any> but got string', 'E712: Argument of extend() must be a List or Dictionary'])
-  CheckDefAndScriptFailure(['extend([1, 2], 3)'], ['E1013: Argument 2: type mismatch, expected list<number> but got number', 'E712: Argument of extend() must be a List or Dictionary'])
+  CheckDefAndScriptFailure(['extend([1, 2], 3)'], ['E1013: Argument 2: type mismatch, expected list<any> but got number', 'E712: Argument of extend() must be a List or Dictionary'])
   CheckDefAndScriptFailure(['var ll = [1, 2]', 'extend(ll, ["x"])'], ['E1013: Argument 2: type mismatch, expected list<number> but got list<string>', 'E1013: Argument 2: type mismatch, expected list<number> but got list<string>'])
   CheckDefFailure(['extend([1, 2], [3], "x")'], 'E1013: Argument 3: type mismatch, expected number but got string')
 
-  CheckDefFailure(['extend({a: 1}, 42)'], 'E1013: Argument 2: type mismatch, expected dict<number> but got number')
-  CheckDefFailure(['extend({a: 1}, {b: "x"})'], 'E1013: Argument 2: type mismatch, expected dict<number> but got dict<string>')
+  CheckDefFailure(['extend({a: 1}, 42)'], 'E1013: Argument 2: type mismatch, expected dict<any> but got number')
   CheckDefFailure(['extend({a: 1}, {b: 2}, 1)'], 'E1013: Argument 3: type mismatch, expected string but got number')
 
-  CheckDefFailure(['extend([1], ["b"])'], 'E1013: Argument 2: type mismatch, expected list<number> but got list<string>')
-  CheckDefExecFailure(['extend([1], ["b", 1])'], 'E1013: Argument 2: type mismatch, expected list<number> but got list<any>')
-
   CheckScriptFailure(['vim9script', 'var l = [1]', 'extend(l, ["b", 1])'], 'E1013: Argument 2: type mismatch, expected list<number> but got list<any> in extend()')
 enddef