--- a/lib/getdate.y
+++ b/lib/getdate.y
@@ -28,6 +28,7 @@
 #endif
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <ctype.h>
 
 #if defined (STDC_HEADERS) || (!defined (isascii) && !defined (HAVE_ISASCII))