--- a/libfreefare/mifare_desfire_crypto.c
+++ b/libfreefare/mifare_desfire_crypto.c
@@ -60,6 +60,7 @@
 #include <err.h>
 #include <string.h>
 #include <strings.h>
+#include <stdlib.h>

 #ifdef WITH_DEBUG
 #  include <libutil.h>