1 files changed, 1 insertions, 1 deletions
diff --git a/array.c b/array.c
index 207d5a337a..f4c3e27af7 100644
--- a/array.c
+++ b/array.c
@@ -2835,7 +2835,7 @@ rb_ary_join_m(int argc, VALUE *argv, VALUE ary)
     if (rb_check_arity(argc, 0, 1) == 0 || NIL_P(sep = argv[0])) {
         sep = rb_output_fs;
         if (!NIL_P(sep)) {
-            rb_warn("$, is set to non-nil value");
+            rb_category_warn(RB_WARN_CATEGORY_DEPRECATED, "$, is set to non-nil value");
         }
     }