diff --git a/modules/users/db_based_user.cpp b/modules/users/db_based_user.cpp
index 2a26085..868e072 100644
--- a/modules/users/db_based_user.cpp
+++ b/modules/users/db_based_user.cpp
@@ -8,6 +8,8 @@
 #include <cstdio>
 
 void DBBasedUser::save() {
+	_mutex.lock();
+
 	QueryBuilder *b = DatabaseManager::get_singleton()->ddb->get_query_builder();
 
 	if (id == 0) {
@@ -77,11 +79,15 @@ void DBBasedUser::save() {
 	b->run_query();
 
 	delete b;
+
+	_mutex.unlock();
 }
 
 void DBBasedUser::load() {
 	unregister_sessions();
 
+	_mutex.lock();
+
 	if (id == 0) {
 		return;
 	}
@@ -128,6 +134,8 @@ void DBBasedUser::load() {
 
 	delete b;
 
+	_mutex.unlock();
+
 	register_sessions();
 }
 
diff --git a/modules/users/user.cpp b/modules/users/user.cpp
index a3ec7cd..b244169 100644
--- a/modules/users/user.cpp
+++ b/modules/users/user.cpp
@@ -74,6 +74,8 @@ void User::register_sessions() {
 		return;
 	}
 
+	_mutex.lock();
+
 	for (int i = 0; i < sessions.size(); ++i) {
 		HTTPSession *session = new HTTPSession();
 		session->session_id = sessions[i];
@@ -81,6 +83,8 @@ void User::register_sessions() {
 
 		sm->add_session(session);
 	}
+
+	_mutex.unlock();
 }
 
 void User::unregister_sessions() {
@@ -95,9 +99,13 @@ void User::unregister_sessions() {
 		return;
 	}
 
+	_mutex.lock();
+
 	for (int i = 0; i < sessions.size(); ++i) {
 		sm->delete_session(sessions[i]);
 	}
+
+	_mutex.unlock();
 }
 
 void User::handle_request_default(Request *request) {
@@ -159,7 +167,11 @@ void User::handle_login_request_default(Request *request) {
 				HTTPSession *session = request->get_or_create_session();
 
 				session->add_object("user", user);
+
+				user->_mutex.lock();
 				user->sessions.push_back(session->session_id);
+				user->_mutex.unlock();
+
 				user->save();
 
 				request->add_cookie(::Cookie("session_id", session->session_id));
@@ -398,7 +410,20 @@ void User::handle_password_reset_request(Request *request) {
 }
 void User::handle_logout_request(Request *request) {
 	request->remove_cookie("session_id");
-	
+
+	_mutex.lock();
+
+	for (int i = 0; i < sessions.size(); ++i) {
+		if (sessions[i] == request->session->session_id) {
+			sessions[i] = sessions[sessions.size() - 1];
+			sessions.pop_back();
+		}
+	}
+
+	_mutex.unlock();
+
+	save();
+
 	SessionManager::get_singleton()->delete_session(request->session->session_id);
 	request->session = nullptr;
 
diff --git a/modules/users/user.h b/modules/users/user.h
index cea439a..5dbdb0d 100644
--- a/modules/users/user.h
+++ b/modules/users/user.h
@@ -5,6 +5,7 @@
 
 #include <string>
 #include <vector>
+#include <mutex>
 
 class Request;
 class FormValidator;
@@ -58,6 +59,8 @@ public:
 
 	static FormValidator *_login_validator;
 	static FormValidator *_registration_validator;
+
+	std::mutex _mutex;
 };
 
 #endif
\ No newline at end of file