diff --git a/src/testdir/test_blob.vim b/src/testdir/test_blob.vim
index 0170f54..e2c332a 100644
--- a/src/testdir/test_blob.vim
+++ b/src/testdir/test_blob.vim
@@ -307,6 +307,9 @@
   call assert_fails('call insert(b, -1)', 'E475:')
   call assert_fails('call insert(b, 257)', 'E475:')
   call assert_fails('call insert(b, 0, [9])', 'E745:')
+  call assert_fails('call insert(b, 0, -20)', 'E475:')
+  call assert_fails('call insert(b, 0, 20)', 'E475:')
+  call assert_fails('call insert(b, [])', 'E745:')
 endfunc
 
 func Test_blob_reverse()