rtbuf/rtbuf

diff --git a/gtk/rtbuf_gtk_library.c b/gtk/rtbuf_gtk_library.c
index da1b23a..aae3bf3 100644
--- a/gtk/rtbuf_gtk_library.c
+++ b/gtk/rtbuf_gtk_library.c
@@ -17,6 +17,7 @@
 #include <assert.h>
 #include <err.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <dirent.h>