diff --git a/tests/vsnprintf_test.cpp b/tests/vsnprintf_test.cpp
index 24a4d20..9b29d5f 100644
--- a/tests/vsnprintf_test.cpp
+++ b/tests/vsnprintf_test.cpp
@@ -8,6 +8,10 @@
 #include <inttypes.h>
 #include <float.h>
 
+#ifndef NAN
+#	define NAN (0.0/0.0)
+#endif // NAN
+
 TEST_CASE("vsnprintf NULL buffer", "No output buffer provided.")
 {
 	REQUIRE(4 == bx::snprintf(NULL, 0, "test") );