diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index ee39680d68..bd47671a22 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -1827,7 +1827,7 @@ static CGroupMask unit_get_disable_mask(Unit *u) {
         return c->disable_controllers;
 }
 
-CGroupMask unit_get_ancestor_disable_mask(Unit *u) {
+static CGroupMask unit_get_ancestor_disable_mask(Unit *u) {
         CGroupMask mask;
         Unit *slice;
 
diff --git a/src/core/cgroup.h b/src/core/cgroup.h
index 4e30434f6d..55669b7e3a 100644
--- a/src/core/cgroup.h
+++ b/src/core/cgroup.h
@@ -376,7 +376,6 @@ CGroupMask unit_get_own_mask(Unit *u);
 CGroupMask unit_get_delegate_mask(Unit *u);
 CGroupMask unit_get_members_mask(Unit *u);
 CGroupMask unit_get_siblings_mask(Unit *u);
-CGroupMask unit_get_ancestor_disable_mask(Unit *u);
 
 CGroupMask unit_get_target_mask(Unit *u);
 CGroupMask unit_get_enable_mask(Unit *u);