diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index d904013..20e4280 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -692,6 +692,7 @@
   call assert_equal(0, count("foo", "O"))
   call assert_equal(2, count("foo", "O", 1))
   call assert_equal(2, count("fooooo", "oo"))
+  call assert_equal(0, count("foo", ""))
 endfunc
 
 func Test_changenr()