diff --git a/include/boost/container_hash/detail/hash_float.hpp b/include/boost/container_hash/detail/hash_float.hpp
index f763428..2245b48 100644
--- a/include/boost/container_hash/detail/hash_float.hpp
+++ b/include/boost/container_hash/detail/hash_float.hpp
@@ -18,6 +18,7 @@
 #include <boost/cstdint.hpp>
 #include <boost/assert.hpp>
 #include <boost/limits.hpp>
+#include <functional> // std::equal_to
 #include <cstring>
 
 #if defined(BOOST_MSVC)