--- stack/stack.c	2002/02/07 23:55:21	1.52
+++ stack/stack.c	2002/02/07 23:56:54	1.53
@@ -205,8 +205,8 @@
   strcpy(new_string, "sx_");	/* Stack eXternal */
   current=new_string+3;
   while(old_string[0] != '\0'){
-    current[0]=validchars[old_string[0]/16];
-    current[1]=validchars[old_string[0]%16];
+    current[0]=validchars[(unsigned char)(old_string[0])/16];
+    current[1]=validchars[(unsigned char)(old_string[0])%16];
     current+=2;
     old_string++;
   }