diff --git a/client_http.hpp b/client_http.hpp
index 7c0b18c..9946dfb 100644
--- a/client_http.hpp
+++ b/client_http.hpp
@@ -216,6 +216,7 @@ namespace SimpleWeb {
     /// If you reuse the io_service for other tasks, use the asynchronous request functions instead.
     /// When requesting Server-Sent Events: will throw on error::eof, please use asynchronous request functions instead.
     std::shared_ptr<Response> request(const std::string &method, const std::string &path = {"/"}, string_view content = {}, const CaseInsensitiveMultimap &header = CaseInsensitiveMultimap()) {
+      start_internal_io_service_handler_thread();
       std::promise<std::shared_ptr<Response>> response_promise;
       std::future<std::shared_ptr<Response>> response_future = response_promise.get_future();
       std::shared_ptr<Response> response;
@@ -251,6 +252,7 @@ namespace SimpleWeb {
     /// If you reuse the io_service for other tasks, use the asynchronous request functions instead.
     /// When requesting Server-Sent Events: will throw on error::eof, please use asynchronous request functions instead.
     std::shared_ptr<Response> request(const std::string &method, const std::string &path, std::istream &content, const CaseInsensitiveMultimap &header = CaseInsensitiveMultimap()) {
+      start_internal_io_service_handler_thread();
       std::promise<std::shared_ptr<Response>> response_promise;
       std::future<std::shared_ptr<Response>> response_future = response_promise.get_future();
       std::shared_ptr<Response> response;
@@ -465,8 +467,7 @@ namespace SimpleWeb {
       port = parsed_host_port.second;
     }
 
-    std::shared_ptr<Connection> get_connection() noexcept {
-      std::shared_ptr<Connection> connection;
+    void start_internal_io_service_handler_thread() noexcept {
       LockGuard lock(connections_mutex);
 
       if(!io_service) {
@@ -477,6 +478,15 @@ namespace SimpleWeb {
           io_service->run();
         }));
       }
+    }
+
+    std::shared_ptr<Connection> get_connection() noexcept {
+      std::shared_ptr<Connection> connection;
+      LockGuard lock(connections_mutex);
+
+      if(!io_service) {
+        io_service = std::make_shared<asio::io_service>();
+      }
 
       for(auto it = connections.begin(); it != connections.end(); ++it) {
         if(!(*it)->in_use) {
diff --git a/tests/io_test.cpp b/tests/io_test.cpp
index 9a96315..d8492dd 100644
--- a/tests/io_test.cpp
+++ b/tests/io_test.cpp
@@ -389,12 +389,16 @@ int main() {
 
   // Test large responses
   {
-    HttpClient client("localhost:8080");
-    client.config.max_response_streambuf_size = 400;
+    // Don't mix synchronous and asynchronous on the same client
+    HttpClient sync_request_client("localhost:8080");
+    HttpClient async_request_client("localhost:8080");
+    sync_request_client.config.max_response_streambuf_size = 400;
+    async_request_client.config.max_response_streambuf_size = 400;
+    async_request_client.io_service = std::make_shared<SimpleWeb::io_context>();
     {
       bool thrown = false;
       try {
-        auto r = client.request("GET", "/long-response");
+        auto r = sync_request_client.request("GET", "/long-response");
       }
       catch(...) {
         thrown = true;
@@ -405,7 +409,7 @@ int main() {
       size_t calls = 0;
       bool end = false;
       std::string content;
-      client.request("GET", "/long-response", [&calls, &content, &end](shared_ptr<HttpClient::Response> response, const SimpleWeb::error_code &ec) {
+      async_request_client.request("GET", "/long-response", [&calls, &content, &end](shared_ptr<HttpClient::Response> response, const SimpleWeb::error_code &ec) {
         ASSERT(!ec);
         content += response->content.string();
         calls++;
@@ -413,8 +417,8 @@ int main() {
           ASSERT(response->content.end == false);
         end = response->content.end;
       });
-      SimpleWeb::restart(*client.io_service);
-      client.io_service->run();
+      SimpleWeb::restart(*async_request_client.io_service);
+      async_request_client.io_service->run();
       ASSERT(content == long_response);
       ASSERT(calls > 2);
       ASSERT(end == true);
@@ -422,15 +426,15 @@ int main() {
     {
       size_t calls = 0;
       std::string content;
-      client.request("GET", "/long-response", [&calls, &content](shared_ptr<HttpClient::Response> response, const SimpleWeb::error_code &ec) {
+      async_request_client.request("GET", "/long-response", [&calls, &content](shared_ptr<HttpClient::Response> response, const SimpleWeb::error_code &ec) {
         if(calls == 0)
           ASSERT(!ec);
         content += response->content.string();
         calls++;
         response->close();
       });
-      SimpleWeb::restart(*client.io_service);
-      client.io_service->run();
+      SimpleWeb::restart(*async_request_client.io_service);
+      async_request_client.io_service->run();
       ASSERT(!content.empty());
       ASSERT(calls >= 2);
     }
@@ -438,12 +442,15 @@ int main() {
 
   // Test client timeout
   {
-    HttpClient client("localhost:8080");
-    client.config.timeout = 2;
+    // Don't mix synchronous and asynchronous on the same client
+    HttpClient sync_request_client("localhost:8080");
+    HttpClient async_request_client("localhost:8080");
+    sync_request_client.config.timeout = 2;
+    async_request_client.config.timeout = 2;
     {
       bool thrown = false;
       try {
-        auto r = client.request("GET", "/work");
+        auto r = sync_request_client.request("GET", "/work");
       }
       catch(...) {
         thrown = true;
@@ -452,12 +459,12 @@ int main() {
     }
     {
       bool call = false;
-      client.request("GET", "/work", [&call](shared_ptr<HttpClient::Response> /*response*/, const SimpleWeb::error_code &ec) {
+      async_request_client.request("GET", "/work", [&call](shared_ptr<HttpClient::Response> /*response*/, const SimpleWeb::error_code &ec) {
         ASSERT(ec);
         call = true;
       });
-      SimpleWeb::restart(*client.io_service);
-      client.io_service->run();
+      SimpleWeb::restart(*async_request_client.io_service);
+      async_request_client.io_service->run();
       ASSERT(call);
     }
   }