diff --git a/lib/user_busy.c b/lib/user_busy.c
index 495fa535..8e80049e 100644
--- a/lib/user_busy.c
+++ b/lib/user_busy.c
@@ -17,6 +17,7 @@
 #include <dirent.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <utmpx.h>
 
 #include "atoi/getnum.h"
 #include "defines.h"