diff --git a/source/math_helper.cpp b/source/math_helper.cpp
index 2511e77..f1f78a2 100644
--- a/source/math_helper.cpp
+++ b/source/math_helper.cpp
@@ -7,6 +7,7 @@
  *
  */
 
+#include <stdlib.h>
 #include <math.h>
 #include <float.h>
 #include <math_helper.h>