diff --git a/include/libtorrent/config.hpp b/include/libtorrent/config.hpp
index 9e01c5f5f..da5766af9 100644
--- a/include/libtorrent/config.hpp
+++ b/include/libtorrent/config.hpp
@@ -47,7 +47,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #endif
 
 #ifndef PRId64
-#ifdef _WIN32
+#ifdef _MSC_VER
 #define PRId64 "I64d"
 #else
 #define PRId64 "lld"