strnlen() is only available from Visual Studio 2005+
diff --git a/src/strnlen.h b/src/strnlen.h
index fdd7fe3..eecfe3c 100644
--- a/src/strnlen.h
+++ b/src/strnlen.h
@@ -7,7 +7,8 @@
#ifndef INCLUDE_strlen_h__
#define INCLUDE_strlen_h__
-#if defined(__MINGW32__) || defined(__sun) || defined(__APPLE__) || defined(__MidnightBSD__)
+#if defined(__MINGW32__) || defined(__sun) || defined(__APPLE__) || defined(__MidnightBSD__) ||\
+ (defined(_MSC_VER) && _MSC_VER < 1500)
# define NO_STRNLEN
#endif