diff --git a/includes/ziti/model_support.h b/includes/ziti/model_support.h
index 11c207f3..79b7aa4f 100644
--- a/includes/ziti/model_support.h
+++ b/includes/ziti/model_support.h
@@ -117,7 +117,7 @@ return rc;\
 int parse_##type##_array(array(type) *a, const char *json, size_t len) { return model_parse_array((void***)a, json, len, &type##_META); }\
 ptr(type) alloc_##type() { return (ptr(type))calloc(1, sizeof(type)); } \
 int cmp_##type(const type *lh, const type *rh) { return model_cmp(lh, rh, &type##_META); }\
-void free_##type(type *v) { model_free(v, &type##_META); } \
+void free_##type(ptr(type) v) { model_free(v, &type##_META); } \
 void free_##type##_array(array(type) *ap) { model_free_array((void***)ap, &type##_META); }                      \
 MODEL_API ssize_t type##_to_json_r(const ptr(type) v, int flags, char *outbuf, size_t max) {                    \
 return model_to_json_r(v, &type##_META, flags, outbuf, max); } \
@@ -202,19 +202,19 @@ typedef struct model_map {
     struct model_impl_s *impl;
 } model_map;
 
-ZITI_FUNC size_t model_map_size(model_map *map);
+ZITI_FUNC size_t model_map_size(const model_map *map);
 
 ZITI_FUNC void *model_map_set(model_map *map, const char *key, void *val);
 
-ZITI_FUNC void *model_map_get(model_map *map, const char *key);
+ZITI_FUNC void *model_map_get(const model_map *map, const char *key);
 
 ZITI_FUNC void *model_map_remove(model_map *map, const char *key);
 
 ZITI_FUNC void model_map_clear(model_map *map, _free_f val_free_func);
 
-ZITI_FUNC model_map_iter model_map_iterator(model_map *map);
+ZITI_FUNC model_map_iter model_map_iterator(const model_map *map);
 
-ZITI_FUNC const char *model_map_it_key(model_map_iter *it);
+ZITI_FUNC const char *model_map_it_key(const model_map_iter *it);
 
 ZITI_FUNC void *model_map_it_value(model_map_iter it);
 
diff --git a/library/model_support.c b/library/model_support.c
index f67aa34e..e4d26d5c 100644
--- a/library/model_support.c
+++ b/library/model_support.c
@@ -50,7 +50,7 @@ limitations under the License.
 
 static int parse_obj(void *obj, const char *json, jsmntok_t *tok, type_meta *meta);
 
-static int model_map_compare(model_map *lh, model_map *rh, type_meta *m);
+static int model_map_compare(const model_map *lh, const model_map *rh, type_meta *m);
 
 jsmntok_t* parse_tokens(jsmn_parser *parser, const char *json, size_t len, size_t *ntok) {
     size_t tok_cap = 256;
@@ -972,7 +972,7 @@ int parse_enum(void *ptr, const char *json, void *tok, const void *enum_type) {
     } else {
         return -1;
     }
-    return 0;
+    return 1;
 }
 
 int json_enum(const void *ptr, void *bufp, int indent, int flags, const void *enum_type) {
@@ -1030,7 +1030,7 @@ static void map_resize_table(model_map* m) {
     }
 }
 
-static struct model_map_entry *find_map_entry(model_map *m, const char *key, uint32_t *hash_out) {
+static struct model_map_entry *find_map_entry(const model_map *m, const char *key, uint32_t *hash_out) {
     uint32_t kh = key_hash(key);
     if (hash_out) {
         *hash_out = kh;
@@ -1046,7 +1046,7 @@ static struct model_map_entry *find_map_entry(model_map *m, const char *key, uin
     return NULL;
 }
 
-size_t model_map_size(model_map *m) {
+size_t model_map_size(const model_map *m) {
     return m->impl ? m->impl->size : 0;
 }
 
@@ -1084,8 +1084,8 @@ void *model_map_set(model_map *m, const char *key, void *val) {
     return NULL;
 }
 
-void* model_map_get(model_map *m, const char* key) {
-    if (m->impl == NULL) {
+void* model_map_get(const model_map *m, const char* key) {
+    if (m == NULL || m->impl == NULL) {
         return NULL;
     }
 
@@ -1128,12 +1128,12 @@ void model_map_clear(model_map *map, _free_f free_func) {
     FREE(map->impl);
 }
 
-model_map_iter model_map_iterator(model_map *m) {
+model_map_iter model_map_iterator(const model_map *m) {
     if (m->impl == NULL) { return NULL; }
     return LIST_FIRST(&m->impl->entries);
 }
 
-const char *model_map_it_key(model_map_iter *it) {
+const char *model_map_it_key(const model_map_iter *it) {
     return it != NULL ? ((struct model_map_entry *) it)->key : NULL;
 }
 
@@ -1158,7 +1158,7 @@ model_map_iter model_map_it_remove(model_map_iter it) {
     return next;
 }
 
-static int model_map_compare(model_map *lh, model_map *rh, type_meta *m) {
+static int model_map_compare(const model_map *lh, const model_map *rh, type_meta *m) {
     null_checks(lh, rh)
 
     int rc = 0;