diff --git a/examples/greet/main.cpp b/examples/greet/main.cpp
index a9bb14e..7357397 100644
--- a/examples/greet/main.cpp
+++ b/examples/greet/main.cpp
@@ -21,6 +21,7 @@
 #include <chrono>
 #include <thread>
 #include <unistd.h>
+#include <iostream>
 
 #if defined(__GNU_LIBRARY__) && ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 17) || __GLIBC__ > 2)
 #	define HasSecureGetenv
diff --git a/include/wrenpp/detail/string_bt.hpp b/include/wrenpp/detail/string_bt.hpp
index 689a651..2ea006e 100644
--- a/include/wrenpp/detail/string_bt.hpp
+++ b/include/wrenpp/detail/string_bt.hpp
@@ -18,9 +18,13 @@
 #ifndef id170B0E6C34D14EBA9B92A35977BDBFB3
 #define id170B0E6C34D14EBA9B92A35977BDBFB3
 
+//#define PRINTABLE_STRING_BT
+
 #include <utility>
 #include <cstddef>
-#include <iostream>
+#if defined(PRINTABLE_STRING_BT)
+#	include <iostream>
+#endif
 #include <stdexcept>
 
 namespace dhandy {
@@ -28,8 +32,10 @@ namespace dhandy {
 		template <std::size_t S, typename Ch=char>
 		class string;
 
+#if defined(PRINTABLE_STRING_BT)
 		template <std::size_t S, typename Ch>
 		std::basic_ostream<Ch>& operator<< ( std::basic_ostream<Ch>& parStream, const string<S, Ch>& parString );
+#endif
 
 		namespace implem {
 			template <std::size_t S, typename Ch> constexpr bool eq (const string<S, Ch>& l, const string<S, Ch>& r);
@@ -37,7 +43,9 @@ namespace dhandy {
 
 		template <std::size_t S, typename Ch>
 		class string {
+#if defined(PRINTABLE_STRING_BT)
 			friend std::ostream& operator<< <>( std::ostream& parStream, const string<S>& parString );
+#endif
 			friend constexpr bool implem::eq<S, Ch> (const string<S, Ch>&, const string<S, Ch>&);
 		public:
 			using value_type = Ch;
@@ -122,11 +130,13 @@ namespace dhandy {
 			return implem::concat(std::make_index_sequence<S + S2 - 1>(), string<S>(m_data), parOther);
 		}
 
+#if defined(PRINTABLE_STRING_BT)
 		template <std::size_t S, typename Ch>
 		inline std::ostream& operator<< (std::ostream& parStream, const string<S, Ch>& parString) {
 			parStream << parString.m_data;
 			return parStream;
 		}
+#endif
 
 		template <std::size_t S, typename Ch>
 		constexpr bool string<S, Ch>::operator== (const string<S, Ch>& other) const {