diff --git a/include/boost/optional/detail/optional_reference_spec.hpp b/include/boost/optional/detail/optional_reference_spec.hpp
index 3be3d33..4940a46 100644
--- a/include/boost/optional/detail/optional_reference_spec.hpp
+++ b/include/boost/optional/detail/optional_reference_spec.hpp
@@ -160,8 +160,7 @@ public:
         throw_exception(bad_optional_access());
     }
 
-    bool operator!() const BOOST_NOEXCEPT { return ptr_ == 0; }
-    BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
+    explicit operator bool() const BOOST_NOEXCEPT { return ptr_ != 0; }
 
     void reset() BOOST_NOEXCEPT { ptr_ = 0; }
 
diff --git a/include/boost/optional/optional.hpp b/include/boost/optional/optional.hpp
index 57ff8ef..72fbd60 100644
--- a/include/boost/optional/optional.hpp
+++ b/include/boost/optional/optional.hpp
@@ -29,7 +29,6 @@
 #include <boost/assert.hpp>
 #include <boost/core/addressof.hpp>
 #include <boost/core/enable_if.hpp>
-#include <boost/core/explicit_operator_bool.hpp>
 #include <boost/core/invoke_swap.hpp>
 #include <boost/core/launder.hpp>
 #include <boost/optional/bad_optional_access.hpp>
diff --git a/test/optional_test_convert_assign.cpp b/test/optional_test_convert_assign.cpp
index f0366dc..5e1ceda 100644
--- a/test/optional_test_convert_assign.cpp
+++ b/test/optional_test_convert_assign.cpp
@@ -25,8 +25,7 @@ struct implicit_bool_conv
 
 struct explicit_bool_conv
 {
-  bool operator!() const BOOST_NOEXCEPT { return false; }
-  BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
+  explicit operator bool() const BOOST_NOEXCEPT { return true; }
 };
 
 template <typename To, typename From>