--- src/money.5.c	2006-11-21 18:19:14.000000000 -0500
+++ src/money.6.c	2006-11-21 18:19:14.000000000 -0500
@@ -10,6 +10,11 @@
 Money *
 money_create (int amount, char *currency)
 {
+  if (amount < 0)
+    {
+      return NULL;
+    }
+
   Money *m = malloc (sizeof (Money));
   if (m == NULL)
     {