diff --git a/lcthw-remnants-2/ex19.c b/lcthw-remnants-2/ex19.c
index 682f8a1..814d734 100644
--- a/lcthw-remnants-2/ex19.c
+++ b/lcthw-remnants-2/ex19.c
@@ -3,11 +3,13 @@
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <assert.h>
 #include "ex19.h"
 
 
 int Monster_attack(void *self, int damage)
 {
+  assert(self != NULL);
   Monster *monster = self;
 
   printf("You attack %s!\n", monster->_(description));
@@ -25,6 +27,7 @@ int Monster_attack(void *self, int damage)
 
 int Monster_init(void *self)
 {
+  assert(self != NULL);
   Monster *monster = self;
   monster->hit_points = 10;
   return 1;
@@ -38,6 +41,7 @@ Object MonsterProto = {
 
 void *Room_move(void *self, Direction direction)
 {
+  assert(self != NULL);
   Room *room = self;
   Room *next = NULL;
 
@@ -68,6 +72,7 @@ void *Room_move(void *self, Direction direction)
 
 int Room_attack(void *self, int damage)
 {
+  assert(self != NULL);
   Room *room = self;
   Monster *monster = room->bad_guy;
 
@@ -89,6 +94,7 @@ Object RoomProto = {
 
 void *Map_move(void *self, Direction direction)
 {
+  assert(self != NULL);
   Map *map = self;
   Room *location = map->location;
   Room *next = NULL;
@@ -104,6 +110,7 @@ void *Map_move(void *self, Direction direction)
 
 int Map_attack(void *self, int damage)
 {
+  assert(self != NULL);
   Map *map = self;
   Room *location = map->location;
 
@@ -113,6 +120,7 @@ int Map_attack(void *self, int damage)
 
 int Map_init(void *self)
 {
+  assert(self != NULL);
   Map *map = self;
 
   // make some rooms for a small map
@@ -149,6 +157,7 @@ Object MapProto = {
 
 int process_input(Map *game)
 {
+  assert(game != NULL);
   printf("\n> ");
 
   char ch = getchar();
@@ -204,6 +213,7 @@ int main(int argc, char *argv[])
 
   // make our map to work with
   Map *game = NEW(Map, "The Hall of the Minotaur.");
+  assert(game != NULL);
 
   printf("You enter the ");
   game->location->_(describe)(game->location);
diff --git a/lcthw-remnants-2/object.c b/lcthw-remnants-2/object.c
index 6f5df17..6e9d18e 100644
--- a/lcthw-remnants-2/object.c
+++ b/lcthw-remnants-2/object.c
@@ -16,6 +16,7 @@ void Object_destroy(void *self)
 
 void Object_describe(void *self)
 {
+  assert(self != NULL);
   Object *obj = self;
   printf("%s.\n", obj->description);
 }
@@ -40,6 +41,8 @@ int Object_attack(void *self, int damage)
 
 void *Object_new(size_t size, Object proto, char *description)
 {
+  assert(description != NULL);
+
   // setup the default functions in case they aren't set
   if(!proto.init) proto.init = Object_init;
   if(!proto.describe) proto.describe = Object_describe;
@@ -50,6 +53,7 @@ void *Object_new(size_t size, Object proto, char *description)
   // this seems weird, but we can make a struct of one size,
   // then point a different pointer at it to "cast" it
   Object *el = calloc(1, size);
+  assert(el != NULL);
   *el = proto;
 
   // copy the description over