diff --git a/haversine_02/src/json/dstring.c b/haversine_02/src/json/dstring.c
index 56d402b..ac2da1e 100644
--- a/haversine_02/src/json/dstring.c
+++ b/haversine_02/src/json/dstring.c
@@ -29,6 +29,10 @@ dstr_t *dstr_with_capacity(u64 capacity) {
 }
 
 dstr_t *dstr_from_string(const char *str) {
+  if (!str) {
+    return NULL;
+  }
+
   u64 length = strlen(str);
 
   u64 capacity = length * CAPACITY_SCALAR;
@@ -46,7 +50,7 @@ dstr_t *dstr_from_string(const char *str) {
 }
 
 void dstr_update(dstr_t **dst, const char *src) {
-  if (!(*dst)) {
+  if (!dst || !(*dst)) {
     return;
   }
 
@@ -78,7 +82,7 @@ void dstr_update(dstr_t **dst, const char *src) {
 }
 
 void dstr_free(dstr_t **str) {
-  if (!(*str)) {
+  if (!str || !(*str)) {
     return;
   }
 
@@ -87,7 +91,7 @@ void dstr_free(dstr_t **str) {
 }
 
 void dstr_concat(dstr_t **dst, const char *src) {
-  if (!(*dst)) {
+  if (!dst || !(*dst)) {
     return;
   }
 
@@ -109,7 +113,7 @@ void dstr_concat(dstr_t **dst, const char *src) {
 }
 
 void dstr_append(dstr_t **dst, char c) {
-  if (!(*dst)) {
+  if (!dst || !(*dst)) {
     return;
   }
 
@@ -125,6 +129,10 @@ void dstr_append(dstr_t **dst, char c) {
 }
 
 void dstr_resize(dstr_t **str) {
+  if (!str || !(*str)) {
+    return;
+  }
+
   u64 capacity = (*str)->size;
 
   dstr_t *tmp = (dstr_t *)realloc(*str, sizeof(dstr_t) + capacity + 1);
diff --git a/haversine_02/src/json/json_entities.c b/haversine_02/src/json/json_entities.c
index 4b7f64e..f95b7ef 100644
--- a/haversine_02/src/json/json_entities.c
+++ b/haversine_02/src/json/json_entities.c
@@ -131,8 +131,16 @@ void free_json(jentity_t **entity) {
     dstr_free(&(entt_ptr->pair.key));
   }
 
+  if (!value) {
+    return;
+  }
+
   switch (value->type) {
   case JVAL_COLLECTION:
+    if (!(value->collection)) {
+      break;
+    }
+
     if (value->collection->begin) {
       free_json(&(value->collection->begin));
     }