diff --git a/src/testdir/test_syntax.vim b/src/testdir/test_syntax.vim
index 8a02185..dc05355 100644
--- a/src/testdir/test_syntax.vim
+++ b/src/testdir/test_syntax.vim
@@ -373,6 +373,7 @@
   call AssertFails('syntax cluster contains=Abc', 'E400:')
   call AssertFails("syntax match Character /'.'", 'E401:')
   call AssertFails("syntax match Character /'.'/a", 'E402:')
+  call assert_fails('syntax sync linecont /\%(/', 'E53:')
   call assert_fails('syntax sync linecont /pat', 'E404:')
   call assert_fails('syntax sync linecont', 'E404:')
   call assert_fails('syntax sync linecont /pat1/ linecont /pat2/', 'E403:')
@@ -382,6 +383,7 @@
   call AssertFails('syntax match ccFoo "Foo" nextgroup=ALLBUT,F', 'E407:')
   call AssertFails('syntax region Block start="{" contains=F,ALLBUT', 'E408:')
   call AssertFails("syntax match Characters contains=a.*x /'.'/", 'E409:')
+  call assert_fails('syntax match Search /abc/ contains=ALLBUT,/\%(/', 'E53:')
 endfunc
 
 func Test_syn_sync()