--- box2d-2.4.1.old/include/box2d/b2_math.h
+++ box2d-2.4.1/include/box2d/b2_math.h
@@ -23,6 +23,7 @@
 #ifndef B2_MATH_H
 #define B2_MATH_H
 
+#include <cmath>
 #include <math.h>
 
 #include "b2_api.h"
@@ -31,7 +32,7 @@
 /// This function is used to ensure that a floating point number is not a NaN or infinity.
 inline bool b2IsValid(float x)
 {
-	return isfinite(x);
+	return std::isfinite(x);
 }
 
 #define	b2Sqrt(x)	sqrtf(x)