diff --git a/src/libraries/box2d/b2_math.h b/src/libraries/box2d/b2_math.h
index 479e667be..64ce86f51 100644
--- a/src/libraries/box2d/b2_math.h
+++ b/src/libraries/box2d/b2_math.h
@@ -31,7 +31,7 @@
 /// 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)