--- src/money.5.c	2020-06-21 15:52:50.000000000 +0000
+++ src/money.6.c	2020-06-21 15:52:50.000000000 +0000
@@ -1,58 +1,65 @@
 /*
  * Check: a unit test framework for C
  * Copyright (C) 2001, 2002 Arien Malec
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the
  * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
  * MA 02110-1301, USA.
  */
 
 #include <stdlib.h>
 #include "money.h"
 
 struct Money
 {
     int amount;
     char *currency;
 };
 
 Money *money_create(int amount, char *currency)
 {
-    Money *m = malloc(sizeof(Money));
+    Money *m;
+
+    if (amount < 0)
+    {
+        return NULL;
+    }
+
+    m = malloc(sizeof(Money));
 
     if (m == NULL)
     {
         return NULL;
     }
 
     m->amount = amount;
     m->currency = currency;
     return m;
 }
 
 int money_amount(Money * m)
 {
     return m->amount;
 }
 
 char *money_currency(Money * m)
 {
     return m->currency;
 }
 
 void money_free(Money * m)
 {
     free(m);
     return;
 }