diff --git a/trabalho-pratico/src/interactive_mode/interactive_mode.c b/trabalho-pratico/src/interactive_mode/interactive_mode.c
index 2334f36..6afdb8e 100644
--- a/trabalho-pratico/src/interactive_mode/interactive_mode.c
+++ b/trabalho-pratico/src/interactive_mode/interactive_mode.c
@@ -82,6 +82,7 @@ void __interactive_mode_load_dataset(database_t **database) {
 
     *database = database_create();
     if (!*database) {
+        *database = NULL;
         activity_messagebox_run("Failed to allocate new database!");
         free(path);
         return;
@@ -90,6 +91,8 @@ void __interactive_mode_load_dataset(database_t **database) {
     /* Load new dataset */
     if (dataset_loader_load(*database, path, NULL, NULL)) {
         activity_messagebox_run("Failed to load dataset! Old data has been discarded.");
+        database_free(*database);
+        *database = NULL;
     } else {
         activity_messagebox_run("Dataset loaded successfully!");
     }
diff --git a/trabalho-pratico/src/queries/query_instance.c b/trabalho-pratico/src/queries/query_instance.c
index fbd739d..69db9b4 100644
--- a/trabalho-pratico/src/queries/query_instance.c
+++ b/trabalho-pratico/src/queries/query_instance.c
@@ -123,7 +123,7 @@ const void *query_instance_get_argument_data(const query_instance_t *query) {
 }
 
 void query_instance_free(query_instance_t *query) {
-    if (query->type) {
+    if (query->type && query->argument_data) {
         const query_type_free_arguments_callback_t free_cb =
             query_type_get_free_arguments_callback(query->type);
         free_cb(query->argument_data);