diff --git a/StanHeaders/inst/include/upstream b/StanHeaders/inst/include/upstream
index 2db1a8b72..4637f9494 160000
--- a/StanHeaders/inst/include/upstream
+++ b/StanHeaders/inst/include/upstream
@@ -1 +1 @@
-Subproject commit 2db1a8b7298bd3f7422de2781baa24346b18dc0e
+Subproject commit 4637f9494db2d48d6dfd573505fe9053d0b4be5c