diff --git a/src/vtfpp/ImageConversion.cpp b/src/vtfpp/ImageConversion.cpp
index a26603f87..f05fac98d 100644
--- a/src/vtfpp/ImageConversion.cpp
+++ b/src/vtfpp/ImageConversion.cpp
@@ -15,6 +15,7 @@
 
 #include <Compressonator.h>
 #include <sourcepp/Macros.h>
+#define _USE_MATH_DEFINES
 #include <sourcepp/Math.h>
 
 #define STB_IMAGE_IMPLEMENTATION