diff --git a/src/testdir/test_blob.vim b/src/testdir/test_blob.vim
index 46f2d61..46370c4 100644
--- a/src/testdir/test_blob.vim
+++ b/src/testdir/test_blob.vim
@@ -772,6 +772,7 @@
   call assert_equal(-1, indexof(b, {i, v -> v == 0x1}))
   call assert_equal(1, indexof(b, "v:val == 0xad"))
   call assert_equal(-1, indexof(b, "v:val == 0xff"))
+  call assert_equal(-1, indexof(b, {_, v -> "v == 0xad"}))
 
   call assert_equal(-1, indexof(0z, "v:val == 0x0"))
   call assert_equal(-1, indexof(test_null_blob(), "v:val == 0xde"))