diff --git a/src/skill.cc b/src/skill.cc
index 1c13a4a..f8b3d9a 100644
--- a/src/skill.cc
+++ b/src/skill.cc
@@ -24,6 +24,7 @@
 #include "trait.h"
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #define SKILLS_MAX_USES_PER_DAY (3)