diff --git a/src/testdir/test_ex_z.vim b/src/testdir/test_ex_z.vim
index 608a36c..6e03b0b 100644
--- a/src/testdir/test_ex_z.vim
+++ b/src/testdir/test_ex_z.vim
@@ -68,7 +68,7 @@
   bw!
 endfunc
 
-func Test_z_bug()
+func Test_z_overflow()
   " This used to access invalid memory as a result of an integer overflow
   " and freeze vim.
   normal ox
@@ -76,3 +76,10 @@
   z777777776666666
   ')
 endfunc
+
+func Test_z_negative_lnum()
+  new
+  z^
+  call assert_equal(1, line('.'))
+  bwipe!
+endfunc