diff --git a/apps/openmw/mwworld/worldimp.cpp b/apps/openmw/mwworld/worldimp.cpp
index 4a29ae1d1..f8c537cce 100644
--- a/apps/openmw/mwworld/worldimp.cpp
+++ b/apps/openmw/mwworld/worldimp.cpp
@@ -1,4 +1,10 @@
 #include "worldimp.hpp"
+
+#ifdef _WIN32 // For M_PI
+#define _USE_MATH_DEFINES
+#include <cmath>
+#endif
+
 #ifdef _WIN32
 #include <boost/tr1/tr1/unordered_map>
 #elif defined HAVE_UNORDERED_MAP
@@ -52,10 +58,6 @@
 #include "esmloader.hpp"
 #include "omwloader.hpp"
 
-#ifdef _WIN32
-#define M_PI 3.14159 // Windows doesn't have this
-#endif
-
 using namespace Ogre;
 
 namespace