diff --git a/src/Session/Session.cc b/src/Session/Session.cc
index fc3a38dde..27f15af21 100644
--- a/src/Session/Session.cc
+++ b/src/Session/Session.cc
@@ -369,6 +369,7 @@ void Session::OnRegisterViewer(const CARTA::RegisterViewer& message, uint16_t ic
     } else {
         type = CARTA::SessionType::RESUMED;
         if (session_id != _id) {
+            spdlog::info("({}) Session setting id to {} (was {}) on resume", fmt::ptr(this), session_id, _id);
             _id = session_id;
             spdlog::info("({}) Session setting id to {}", fmt::ptr(this), session_id);
             status = fmt::format("Start a new backend and assign it with session id {}", session_id);
diff --git a/src/Session/Session.h b/src/Session/Session.h
index 255906cc7..056821bd6 100644
--- a/src/Session/Session.h
+++ b/src/Session/Session.h
@@ -288,9 +288,6 @@ class Session {
     void SendFileEvent(
         int file_id, CARTA::EventType event_type, u_int32_t event_id, google::protobuf::MessageLite& message, bool compress = true);
     void SendLogEvent(const std::string& message, std::vector<std::string> tags, CARTA::ErrorSeverity severity);
-    void StartAnimationThread() {
-        // Not sure if needed... XXX
-    }
 
     // uWebSockets
     uWS::WebSocket<false, true, PerSocketData>* _socket;
diff --git a/src/Session/SessionManager.cc b/src/Session/SessionManager.cc
index c7a6c8678..e930d5c8c 100644
--- a/src/Session/SessionManager.cc
+++ b/src/Session/SessionManager.cc
@@ -5,10 +5,9 @@
 */
 
 #include "SessionManager.h"
-#include "ThreadingManager/ThreadingManager.h"
-
 #include "Logger/Logger.h"
 #include "OnMessageTask.h"
+#include "ThreadingManager/ThreadingManager.h"
 #include "Util/Message.h"
 #include "Util/Token.h"
 
@@ -17,7 +16,7 @@ namespace carta {
 SessionManager::SessionManager(ProgramSettings& settings, std::string auth_token, std::shared_ptr<FileListHandler> file_list_handler)
     : _session_number(0), _app(uWS::App()), _settings(settings), _auth_token(auth_token), _file_list_handler(file_list_handler) {}
 
-void SessionManager::DeleteSession(int session_id) {
+void SessionManager::DeleteSession(uint32_t session_id) {
     Session* session = _sessions[session_id];
     if (session) {
         spdlog::info(
@@ -57,9 +56,11 @@ void SessionManager::OnUpgrade(
         return;
     }
 
-    _session_number++;
-    // protect against overflow
-    _session_number = max(_session_number, 1u);
+    auto now = std::chrono::system_clock::now();
+    auto now_ms = std::chrono::time_point_cast<std::chrono::microseconds>(now);
+    auto epoch = now_ms.time_since_epoch();
+    auto value = std::chrono::duration_cast<std::chrono::microseconds>(epoch);
+    _session_number = value.count();
 
     http_response->template upgrade<PerSocketData>({_session_number, address}, //
         http_request->getHeader("sec-websocket-key"),                          //
@@ -103,8 +104,10 @@ void SessionManager::OnDisconnect(WSType* ws, int code, std::string_view message
     uint32_t session_id = static_cast<PerSocketData*>(ws->getUserData())->session_id;
 
     // Delete the Session
-    _sessions[session_id]->DecreaseRefCount();
-    DeleteSession(session_id);
+    if (_sessions.count(session_id) > 0) {
+        _sessions[session_id]->DecreaseRefCount();
+        DeleteSession(session_id);
+    }
 
     // Close the websockets
     ws->close();
diff --git a/src/Session/SessionManager.h b/src/Session/SessionManager.h
index 3de158a59..fdc33f674 100644
--- a/src/Session/SessionManager.h
+++ b/src/Session/SessionManager.h
@@ -20,7 +20,7 @@ class SessionManager {
 public:
     using WSType = uWS::WebSocket<false, true, PerSocketData>;
     SessionManager(ProgramSettings& settings, std::string auth_token, std::shared_ptr<FileListHandler>);
-    void DeleteSession(int session_id);
+    void DeleteSession(uint32_t session_id);
     void OnUpgrade(uWS::HttpResponse<false>* http_response, uWS::HttpRequest* http_request, struct us_socket_context_t* context);
     // Called on connection. Creates session objects and assigns UUID to it
     void OnConnect(WSType* ws);