diff --git a/src/util.h b/src/util.h
index bbdb150..b7c77e4 100644
--- a/src/util.h
+++ b/src/util.h
@@ -48,6 +48,7 @@ void *ccalloc(size_t num, size_t size);
 #define MAX SDL_max
 #define MIN SDL_min
 
+#define M_PI 3.14159265358979323846264338327950288   /**< pi */
 
 /* sets buf_out to a pointer to a byte buffer which must be freed. */
 /* returns the size of this buffer. */