diff --git a/ex19.c b/ex19.c
index 1d73d2f..5acd311 100644
--- a/ex19.c
+++ b/ex19.c
@@ -3,11 +3,15 @@
 #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);
+    assert(damage > -1);
+
     Monster *monster = self;
 
     printf("You attack %s!\n", monster->_(description));
@@ -25,6 +29,8 @@ int Monster_attack(void *self, int damage)
 
 int Monster_init(void *self)
 {
+    assert(self != NULL);
+
     Monster *monster = self;
     monster->hit_points = 10;
     return 1;
@@ -39,6 +45,9 @@ Object MonsterProto = {
 
 void *Room_move(void *self, Direction direction)
 {
+    assert(self != NULL);
+    assert(direction);
+
     Room *room = self;
     Room *next = NULL;
 
@@ -69,6 +78,9 @@ void *Room_move(void *self, Direction direction)
 
 int Room_attack(void *self, int damage)
 {
+    assert(self != NULL);
+    assert(damage > -1);
+
     Room *room = self;
     Monster *monster = room->bad_guy;
 
@@ -90,6 +102,9 @@ Object RoomProto = {
 
 void *Map_move(void *self, Direction direction)
 {
+    assert(self != NULL);
+    assert(direction);
+
     Map *map = self;
     Room *location = map->location;
     Room *next = NULL;
@@ -106,6 +121,9 @@ void *Map_move(void *self, Direction direction)
 
 int Map_attack(void *self, int damage)
 {
+    assert(self != NULL);
+    assert(damage > -1);
+
     Map *map = self;
     Room *location = map->location;
 
@@ -115,6 +133,8 @@ 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
@@ -156,12 +176,13 @@ int process_input(Map *game)
     printf("\n> ");
 
     char ch = getchar();
+    assert(ch != EOF);
     getchar(); // eat ENTER
 
     int damage = rand() % 4;
 
     switch(ch) {
-        case -1:
+        case EOF:
             printf("Giving up?  You suck.\n");
             return 0;
             break;
diff --git a/object.c b/object.c
index 07a5af5..268f169 100644
--- a/object.c
+++ b/object.c
@@ -7,6 +7,8 @@
 
 void Object_destroy(void *self)
 {
+    assert(self != NULL);
+
     Object *obj = self;
 
     if(obj) {
@@ -18,6 +20,8 @@ void Object_destroy(void *self)
 
 void Object_describe(void *self)
 {
+    assert(self != NULL);
+
     Object *obj = self;
     printf("%s\n", obj->description);
 }
@@ -25,6 +29,8 @@ void Object_describe(void *self)
 
 int Object_init(void *self)
 {
+    assert(self != NULL);
+
     // do nothing really
     return 1;
 }
@@ -32,6 +38,9 @@ int Object_init(void *self)
 
 void *Object_move(void *self, Direction direction)
 {
+    assert(self != NULL);
+    assert(direction);
+
     printf("You can't go that direction.\n");
     return NULL;
 }
@@ -39,6 +48,9 @@ void *Object_move(void *self, Direction direction)
 
 int Object_attack(void *self, int damage)
 {
+    assert(self != NULL);
+    assert(damage);
+
     printf("You can't attack that.\n");
     return 0;
 }
@@ -46,7 +58,9 @@ int Object_attack(void *self, int damage)
 
 void *Object_new(size_t size, Object proto, char *description)
 {
+    assert(size);
     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;
@@ -62,6 +76,7 @@ void *Object_new(size_t size, Object proto, char *description)
 
     // copy the description over
     el->description = strdup(description);
+    assert(el->description != NULL);
 
     // initialize it with whatever init we were given
     if(!el->init(el)) {