diff --git a/StanHeaders/inst/include/upstream b/StanHeaders/inst/include/upstream
index 677398998..51dbaa4a4 160000
--- a/StanHeaders/inst/include/upstream
+++ b/StanHeaders/inst/include/upstream
@@ -1 +1 @@
-Subproject commit 677398998e7907c83d4cc8189a5ad4ade8cd2b34
+Subproject commit 51dbaa4a4aa5b8d1605b3bbee43f31e297546fbf