diff --git a/liblights/lights.c b/liblights/lights.c
index a1cad47..516723b 100644
--- a/liblights/lights.c
+++ b/liblights/lights.c
@@ -23,6 +23,7 @@
 #include <sched.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <time.h>