diff --git a/src/testdir/test_json.vim b/src/testdir/test_json.vim
index c3b4382..c619882 100644
--- a/src/testdir/test_json.vim
+++ b/src/testdir/test_json.vim
@@ -201,6 +201,8 @@
   call assert_fails('call json_decode("\"\\u111Z\"")', 'E491:')
   call assert_equal('[😂]', json_decode('"[\uD83D\uDE02]"'))
   call assert_equal('a😂b', json_decode('"a\uD83D\uDE02b"'))
+
+  call assert_fails('call json_decode("{\"\":{\"\":{")', 'E491:')
 endfunc
 
 let s:jsl5 = '[7,,,]'