diff --git a/src/testdir/test64.in b/src/testdir/test64.in
index 2df9a6b..77949c5 100644
--- a/src/testdir/test64.in
+++ b/src/testdir/test64.in
@@ -406,6 +406,7 @@
 :call add(tl, [2, '^.*\.\(.*\)/.\+\(\1\)\@<!$', 'foo.bat/foo.bat'])
 :call add(tl, [2, '^.*\.\(.*\)/.\+\(\1\)\@<=$', 'foo.bat/foo.bat', 'foo.bat/foo.bat', 'bat', 'bat'])
 :call add(tl, [2, '\\\@<!\${\(\d\+\%(:.\{-}\)\?\\\@<!\)}', '2013-06-27${0}', '${0}', '0'])
+:call add(tl, [2, '^\(a*\)\1$', 'aaaaaaaa', 'aaaaaaaa', 'aaaa'])
 :"
 :"""" Look-behind with limit
 :call add(tl, [2, '<\@<=span.', 'xxspanxx<spanyyy', 'spany'])