diff --git a/include/xo/alloc2/arena/ArenaConfig.hpp b/include/xo/alloc2/arena/ArenaConfig.hpp
index c8d3fac..fcd9534 100644
--- a/include/xo/alloc2/arena/ArenaConfig.hpp
+++ b/include/xo/alloc2/arena/ArenaConfig.hpp
@@ -35,7 +35,7 @@ namespace xo {
              **/
             bool store_header_flag_ = false;
             /** configuration for per-alloc header **/
-            AllocHeaderConfig header_;
+            AllocHeaderConfig header_{};
             /** true to enable debug logging **/
             bool debug_flag_ = false;