diff --git a/freewnn-utils.c b/freewnn-utils.c
index 3cf63b3..0e871d6 100644
--- a/freewnn-utils.c
+++ b/freewnn-utils.c
@@ -18,6 +18,9 @@
  * Boston, MA 02111-1307, USA.
  */
 
+#include <stdlib.h>
+#include <string.h>
+
 #include "freewnn-utils.h"
 #include "kata2hkata.h"
 
diff --git a/im-freewnn.c b/im-freewnn.c
index b56d63c..833582e 100644
--- a/im-freewnn.c
+++ b/im-freewnn.c
@@ -26,6 +26,7 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 
 #include <string.h>
 #include "keytable.h"