diff --git a/lib/cpp/test/ZlibTest.cpp b/lib/cpp/test/ZlibTest.cpp
index a4387a9..25db4b8 100644
--- a/lib/cpp/test/ZlibTest.cpp
+++ b/lib/cpp/test/ZlibTest.cpp
@@ -21,7 +21,7 @@
 #define _GNU_SOURCE // needed for getopt_long
 #endif
 
-#if (_MSC_VER <= 1700)
+#if defined(_MSC_VER) && (_MSC_VER <= 1700)
 // polynomial and std::fill_t warning happens in MSVC 2010, 2013, maybe others
 // https://svn.boost.org/trac/boost/ticket/11426
 #pragma warning(disable:4996)