diff --git a/machine_learning/adaline_learning.cpp b/machine_learning/adaline_learning.cpp
index b29813984..29eccd886 100644
--- a/machine_learning/adaline_learning.cpp
+++ b/machine_learning/adaline_learning.cpp
@@ -22,6 +22,7 @@
 
 #include <cassert>
 #include <climits>
+#include <cstdlib>
 #include <ctime>
 #include <iostream>
 #include <vector>