diff --git a/inst/tests/tests.Rraw b/inst/tests/tests.Rraw
index e01c4736c..a407d7e94 100644
--- a/inst/tests/tests.Rraw
+++ b/inst/tests/tests.Rraw
@@ -18749,6 +18749,6 @@ DT1 = data.table(a=1:2)
 DT2 = data.table(a=c(1, 1, 2, 2), b=1:4)
 test(2271, options=c(datatable.verbose=TRUE), copy(DT1)[DT2, on='a', v := 4], copy(DT1)[, v := 4], output="x.a.\nAssigning")
 
-# shift of many elements accumulated PROTECT() for the fill values instead of releasing as soon as possible
+# shift of many elements accumulated PROTECT() for the fill values instead of releasing as soon as possible. Spotted by rchk in #6257.
 l = as.list(seq_len(2e4))
 test(2272, shift(l), as.list(rep(NA_integer_, 2e4)))