diff --git a/include/pybind11/detail/smart_holder_poc.h b/include/pybind11/detail/smart_holder_poc.h
index 65b0581617..91873ab346 100644
--- a/include/pybind11/detail/smart_holder_poc.h
+++ b/include/pybind11/detail/smart_holder_poc.h
@@ -54,6 +54,7 @@ High-level aspects:
 #include <string>
 #include <type_traits>
 #include <typeinfo>
+#include <utility>
 
 // pybindit = Python Bindings Innovation Track.
 // Currently not in pybind11 namespace to signal that this POC does not depend