diff --git a/sprout/complex/transcendentals.hpp b/sprout/complex/transcendentals.hpp
index c18474e0..57a96cbf 100644
--- a/sprout/complex/transcendentals.hpp
+++ b/sprout/complex/transcendentals.hpp
@@ -219,16 +219,16 @@ namespace sprout {
 	inline SPROUT_CONSTEXPR sprout::complex<T> log10(sprout::complex<T> const& x) {
 		return sprout::log(x) / sprout::log(T(10));
 	}
+
+	//
+	// pow
+	//
 	namespace detail {
 		template<typename T>
 		inline SPROUT_CONSTEXPR sprout::complex<T> pow_impl(sprout::complex<T> const& t, T const& y) {
 			return sprout::polar(sprout::exp(y * t.real()), y * t.imag());
 		}
 	}	// namespace detail
-
-	//
-	// pow
-	//
 	template<typename T>
 	inline SPROUT_CONSTEXPR sprout::complex<T>
 	pow(sprout::complex<T> const& x, T const& y) {
@@ -295,11 +295,6 @@ namespace sprout {
 			return sprout::detail::sqrt_impl_2_1(x, t, t / 2);
 		}
 	}	// namespace detail
-
-	//
-	// tan
-	// tanh
-	//
 	template<typename T>
 	inline SPROUT_CONSTEXPR sprout::complex<T>
 	sqrt(sprout::complex<T> const& x) {
@@ -307,6 +302,11 @@ namespace sprout {
 			: sprout::detail::sqrt_impl_2(x, sprout::sqrt(2 * (sprout::abs(x) + sprout::abs(x.real()))))
 			;
 	}
+
+	//
+	// tan
+	// tanh
+	//
 	template<typename T>
 	inline SPROUT_CONSTEXPR sprout::complex<T>
 	tan(sprout::complex<T> const& x) {
diff --git a/sprout/config/suffix.hpp b/sprout/config/suffix.hpp
index f1850f34..42167652 100644
--- a/sprout/config/suffix.hpp
+++ b/sprout/config/suffix.hpp
@@ -47,11 +47,14 @@
 
 //
 // SPROUT_USE_EXPLICIT_CONVERSION_OPERATORS
+// SPROUT_EXPLICIT_CONVERSION
 //
 #ifndef SPROUT_CONFIG_DISABLE_EXPLICIT_CONVERSION_OPERATORS
 #	define SPROUT_USE_EXPLICIT_CONVERSION_OPERATORS 1
+#	define SPROUT_EXPLICIT_CONVERSION explicit
 #else	// #ifndef SPROUT_CONFIG_DISABLE_EXPLICIT_CONVERSION_OPERATORS
 #	define SPROUT_USE_EXPLICIT_CONVERSION_OPERATORS 0
+#	define SPROUT_EXPLICIT_CONVERSION
 #endif	// #ifndef SPROUT_CONFIG_DISABLE_EXPLICIT_CONVERSION_OPERATORS
 
 //
diff --git a/sprout/optional/optional.hpp b/sprout/optional/optional.hpp
index 38a6654b..93089a2d 100644
--- a/sprout/optional/optional.hpp
+++ b/sprout/optional/optional.hpp
@@ -294,7 +294,7 @@ namespace sprout {
 				;
 		}
 
-		SPROUT_CONSTEXPR operator bool() const SPROUT_NOEXCEPT {
+		SPROUT_EXPLICIT_CONVERSION SPROUT_CONSTEXPR operator bool() const SPROUT_NOEXCEPT {
 			return is_initialized();
 		}
 		SPROUT_CONSTEXPR bool operator!() const SPROUT_NOEXCEPT {
diff --git a/sprout/string/string.hpp b/sprout/string/string.hpp
index c020b2a2..afcf23a5 100644
--- a/sprout/string/string.hpp
+++ b/sprout/string/string.hpp
@@ -493,12 +493,10 @@ namespace sprout {
 				sprout::make_index_tuple<N2>::make()
 				);
 		}
-#if SPROUT_USE_EXPLICIT_CONVERSION_OPERATORS
 		template<typename Allocator>
-		explicit operator std::basic_string<T, Traits, Allocator>() const {
+		SPROUT_EXPLICIT_CONVERSION operator std::basic_string<T, Traits, Allocator>() const {
 			return std::basic_string<T, Traits, Allocator>(data(), size());
 		}
-#endif
 		pointer
 		c_array() SPROUT_NOEXCEPT {
 			return &elems[0];
diff --git a/sprout/utility/string_ref/string_ref.hpp b/sprout/utility/string_ref/string_ref.hpp
index 32e1260f..660ea221 100644
--- a/sprout/utility/string_ref/string_ref.hpp
+++ b/sprout/utility/string_ref/string_ref.hpp
@@ -390,12 +390,10 @@ namespace sprout {
 			return size() >= str.size() && traits_type::compare(data() + size() - str.size(), str.data(), str.size()) == 0;
 		}
 		// others:
-#if SPROUT_USE_EXPLICIT_CONVERSION_OPERATORS
 		template<typename Allocator>
-		explicit operator std::basic_string<T, Traits, Allocator>() const {
+		SPROUT_EXPLICIT_CONVERSION operator std::basic_string<T, Traits, Allocator>() const {
 			return std::basic_string<T, Traits, Allocator>(data(), size());
 		}
-#endif
 		pointer
 		c_array() SPROUT_NOEXCEPT {
 			return data();