diff --git a/server_http.hpp b/server_http.hpp
index 1eb5722..ab4be0e 100644
--- a/server_http.hpp
+++ b/server_http.hpp
@@ -386,6 +386,8 @@ namespace SimpleWeb {
     /// Returns assigned port. If io_service is not set, an internal io_service is created instead.
     /// Call before accept_and_run().
     unsigned short bind() {
+      std::lock_guard<std::mutex> lock(start_stop_mutex);
+
       asio::ip::tcp::endpoint endpoint;
       if(config.address.size() > 0)
         endpoint = asio::ip::tcp::endpoint(make_address(config.address), config.port);
@@ -452,6 +454,8 @@ namespace SimpleWeb {
 
     /// Stop accepting new requests, and close current connections.
     void stop() noexcept {
+      std::lock_guard<std::mutex> lock(start_stop_mutex);
+
       if(acceptor) {
         error_code ec;
         acceptor->close(ec);
@@ -474,6 +478,8 @@ namespace SimpleWeb {
     }
 
   protected:
+    std::mutex start_stop_mutex;
+
     bool internal_io_service = false;
 
     std::unique_ptr<asio::ip::tcp::acceptor> acceptor;