diff --git a/src/r_poly_intersection.h b/src/r_poly_intersection.h
index 16f30201c2..48ebef0314 100644
--- a/src/r_poly_intersection.h
+++ b/src/r_poly_intersection.h
@@ -24,6 +24,7 @@
 
 #include "r_triangle.h"
 #include <algorithm>
+#include <cmath>
 
 class Vec4f
 {