diff --git a/src/microhttpd/test_client_put_stop.c b/src/microhttpd/test_client_put_stop.c
index 388bc12d..aaf5c829 100644
--- a/src/microhttpd/test_client_put_stop.c
+++ b/src/microhttpd/test_client_put_stop.c
@@ -1979,7 +1979,8 @@ startTestMhdDaemon (enum testMhdThreadsType thrType,
 
   if (testMhdThreadExternal == thrType)
     d = MHD_start_daemon (((unsigned int) pollType)
-                          | (verbose ? MHD_USE_ERROR_LOG : 0),
+                          | (verbose ? MHD_USE_ERROR_LOG : 0)
+                          | MHD_USE_NO_THREAD_SAFETY,
                           *pport, NULL, NULL,
                           &ahcCheck, *ahc_param,
                           MHD_OPTION_URI_LOG_CALLBACK, &check_uri_cb,
diff --git a/src/microhttpd/test_daemon.c b/src/microhttpd/test_daemon.c
index 00c83c63..9239ada5 100644
--- a/src/microhttpd/test_daemon.c
+++ b/src/microhttpd/test_daemon.c
@@ -116,14 +116,15 @@ testStartStop (void)
 
 
 static unsigned int
-testExternalRun (void)
+testExternalRun (int use_no_thread_safe)
 {
   struct MHD_Daemon *d;
   fd_set rs;
   MHD_socket maxfd;
   int i;
 
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG
+                        | (use_no_thread_safe ? MHD_USE_NO_THREAD_SAFETY : 0),
                         0,
                         &apc_all, NULL,
                         &ahc_nothing, NULL,
@@ -233,7 +234,9 @@ main (int argc,
   errorCount += testStartError ();
   if (has_threads_support)
     errorCount += testStartStop ();
-  errorCount += testExternalRun ();
+  if (has_threads_support)
+    errorCount += testExternalRun (0);
+  errorCount += testExternalRun (! 0);
   if (has_threads_support)
   {
     errorCount += testThread ();
diff --git a/src/microhttpd/test_options.c b/src/microhttpd/test_options.c
index 7be7666d..9e2d3b45 100644
--- a/src/microhttpd/test_options.c
+++ b/src/microhttpd/test_options.c
@@ -102,7 +102,7 @@ test_ip_addr_option (void)
 
   ret = 0;
 
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR, &daemon_ip_addr,
                         MHD_OPTION_END);
@@ -120,7 +120,7 @@ test_ip_addr_option (void)
 
 
   daemon_ip_addr.sin_port = htons (port4);
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR_LEN,
                         (socklen_t) sizeof(daemon_ip_addr), &daemon_ip_addr,
@@ -138,7 +138,7 @@ test_ip_addr_option (void)
   MHD_stop_daemon (d);
 
 
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR_LEN,
                         (socklen_t) (sizeof(daemon_ip_addr) / 2),
@@ -154,7 +154,7 @@ test_ip_addr_option (void)
 #ifdef HAVE_STRUCT_SOCKADDR_IN_SIN_LEN
 
   daemon_ip_addr.sin_len = (socklen_t) sizeof(daemon_ip_addr);
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR_LEN,
                         (socklen_t) sizeof(daemon_ip_addr), &daemon_ip_addr,
@@ -173,7 +173,7 @@ test_ip_addr_option (void)
 
 
   daemon_ip_addr.sin_len = (socklen_t) (sizeof(daemon_ip_addr) / 2);
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR_LEN,
                         (socklen_t) sizeof(daemon_ip_addr), &daemon_ip_addr,
@@ -189,7 +189,8 @@ test_ip_addr_option (void)
 
 
 #if defined(HAVE_INET6) && defined(USE_IPV6_TESTING)
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_IPv6, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_IPv6
+                        | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR, &daemon_ip_addr6,
                         MHD_OPTION_END);
@@ -207,7 +208,7 @@ test_ip_addr_option (void)
 
 
   daemon_ip_addr6.sin6_port = htons (port6);
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR_LEN,
                         (socklen_t) sizeof(daemon_ip_addr6), &daemon_ip_addr6,
@@ -225,7 +226,7 @@ test_ip_addr_option (void)
   MHD_stop_daemon (d);
 
 
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR_LEN,
                         (socklen_t) (sizeof(daemon_ip_addr6) / 2),
@@ -241,7 +242,7 @@ test_ip_addr_option (void)
 #if defined(HAVE_STRUCT_SOCKADDR_IN6_SIN6_LEN)
 
   daemon_ip_addr6.sin6_len = (socklen_t) sizeof(daemon_ip_addr6);
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR_LEN,
                         (socklen_t) sizeof(daemon_ip_addr6), &daemon_ip_addr6,
@@ -260,7 +261,7 @@ test_ip_addr_option (void)
 
 
   daemon_ip_addr6.sin6_len = (socklen_t) (sizeof(daemon_ip_addr6) / 2);
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG, 0,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY, 0,
                         NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_SOCK_ADDR_LEN,
                         (socklen_t) sizeof(daemon_ip_addr6), &daemon_ip_addr6,
diff --git a/src/microhttpd/test_set_panic.c b/src/microhttpd/test_set_panic.c
index cec361f6..ca9a0375 100644
--- a/src/microhttpd/test_set_panic.c
+++ b/src/microhttpd/test_set_panic.c
@@ -1469,7 +1469,8 @@ startTestMhdDaemon (enum testMhdThreadsType thrType,
 
   if (testMhdThreadExternal == thrType)
     d = MHD_start_daemon (((unsigned int) pollType)
-                          | (verbose ? MHD_USE_ERROR_LOG : 0),
+                          | (verbose ? MHD_USE_ERROR_LOG : 0)
+                          | MHD_USE_NO_THREAD_SAFETY,
                           *pport, NULL, NULL,
                           &ahcCheck, *ahc_param,
                           MHD_OPTION_NOTIFY_CONNECTION, &socket_cb,
diff --git a/src/microhttpd/test_start_stop.c b/src/microhttpd/test_start_stop.c
index a64f3011..1031e12e 100644
--- a/src/microhttpd/test_start_stop.c
+++ b/src/microhttpd/test_start_stop.c
@@ -101,9 +101,6 @@ testMultithreadedPoolGet (unsigned int poll_flag)
 }
 
 
-#endif
-
-
 static unsigned int
 testExternalGet (void)
 {
@@ -120,6 +117,25 @@ testExternalGet (void)
 }
 
 
+#endif
+
+
+static unsigned int
+testExternalGetSingleThread (void)
+{
+  struct MHD_Daemon *d;
+
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
+                        0, NULL, NULL,
+                        &ahc_echo, NULL,
+                        MHD_OPTION_END);
+  if (NULL == d)
+    return 8;
+  MHD_stop_daemon (d);
+  return 0;
+}
+
+
 int
 main (int argc,
       char *const *argv)
@@ -132,8 +148,9 @@ main (int argc,
   errorCount += testInternalGet (0);
   errorCount += testMultithreadedGet (0);
   errorCount += testMultithreadedPoolGet (0);
-#endif
   errorCount += testExternalGet ();
+#endif
+  errorCount += testExternalGetSingleThread ();
 #if defined(MHD_USE_POSIX_THREADS) || defined(MHD_USE_W32_THREADS)
   if (MHD_YES == MHD_is_feature_supported (MHD_FEATURE_POLL))
   {
diff --git a/src/microhttpd/test_upgrade.c b/src/microhttpd/test_upgrade.c
index 0abd5f10..22b15090 100644
--- a/src/microhttpd/test_upgrade.c
+++ b/src/microhttpd/test_upgrade.c
@@ -1275,7 +1275,8 @@ test_upgrade (unsigned int flags,
   done = false;
 
   if (! test_tls)
-    d = MHD_start_daemon (flags | MHD_USE_ERROR_LOG | MHD_ALLOW_UPGRADE,
+    d = MHD_start_daemon (flags | MHD_USE_ERROR_LOG | MHD_ALLOW_UPGRADE
+                          | MHD_USE_ITC,
                           global_port,
                           NULL, NULL,
                           &ahc_upgrade, NULL,
@@ -1289,7 +1290,7 @@ test_upgrade (unsigned int flags,
 #ifdef HTTPS_SUPPORT
   else
     d = MHD_start_daemon (flags | MHD_USE_ERROR_LOG | MHD_ALLOW_UPGRADE
-                          | MHD_USE_TLS,
+                          | MHD_USE_TLS | MHD_USE_ITC,
                           global_port,
                           NULL, NULL,
                           &ahc_upgrade, NULL,
diff --git a/src/testcurl/https/test_https_get_select.c b/src/testcurl/https/test_https_get_select.c
index 1939ccff..8ce55e2c 100644
--- a/src/testcurl/https/test_https_get_select.c
+++ b/src/testcurl/https/test_https_get_select.c
@@ -278,7 +278,9 @@ main (int argc, char *const *argv)
 #ifdef EPOLL_SUPPORT
   errorCount += testExternalGet (MHD_USE_EPOLL);
 #endif
-  errorCount += testExternalGet (0);
+  if (MHD_YES == MHD_is_feature_supported (MHD_FEATURE_THREADS))
+    errorCount += testExternalGet (MHD_NO_FLAG);
+  errorCount += testExternalGet (MHD_USE_NO_THREAD_SAFETY);
   curl_global_cleanup ();
   if (errorCount != 0)
     fprintf (stderr, "Failed test: %s, error: %u.\n", argv[0], errorCount);
diff --git a/src/testcurl/perf_get.c b/src/testcurl/perf_get.c
index 0a8af562..c9f400a3 100644
--- a/src/testcurl/perf_get.c
+++ b/src/testcurl/perf_get.c
@@ -458,7 +458,7 @@ testExternalGet (uint16_t port)
   multi = NULL;
   cbc.buf = buf;
   cbc.size = 2048;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL,
                         &ahc_echo, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_add_conn.c b/src/testcurl/test_add_conn.c
index 4fd651b3..2539b5f5 100644
--- a/src/testcurl/test_add_conn.c
+++ b/src/testcurl/test_add_conn.c
@@ -739,8 +739,7 @@ startTestMhdDaemon (enum testMhdThreadsType thrType,
 
   if (testMhdThreadExternal == thrType)
     d = MHD_start_daemon (((unsigned int) thrType) | ((unsigned int) pollType)
-                          | (thrType == testMhdThreadExternal ?
-                             0 : MHD_USE_ITC)
+                          | MHD_USE_NO_THREAD_SAFETY
                           | (no_listen ? MHD_USE_NO_LISTEN_SOCKET : 0)
                           | MHD_USE_ERROR_LOG,
                           *pport, NULL, NULL,
diff --git a/src/testcurl/test_basicauth.c b/src/testcurl/test_basicauth.c
index 963639c9..d6fe1427 100644
--- a/src/testcurl/test_basicauth.c
+++ b/src/testcurl/test_basicauth.c
@@ -647,7 +647,7 @@ testBasicAuth (void)
   else
     port = 4210;
 
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL,
                         &ahc_echo, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_callback.c b/src/testcurl/test_callback.c
index 510043cc..3cc28c5f 100644
--- a/src/testcurl/test_callback.c
+++ b/src/testcurl/test_callback.c
@@ -141,7 +141,7 @@ main (int argc, char **argv)
   else
     port = 1140;
 
-  d = MHD_start_daemon (0,
+  d = MHD_start_daemon (MHD_USE_NO_THREAD_SAFETY,
                         port,
                         NULL,
                         NULL,
diff --git a/src/testcurl/test_delete.c b/src/testcurl/test_delete.c
index 681afe30..81fa9986 100644
--- a/src/testcurl/test_delete.c
+++ b/src/testcurl/test_delete.c
@@ -389,7 +389,7 @@ testExternalDelete (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port,
                         NULL, NULL, &ahc_echo, &done_flag,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_digestauth2.c b/src/testcurl/test_digestauth2.c
index e94f7b63..2ec78e26 100644
--- a/src/testcurl/test_digestauth2.c
+++ b/src/testcurl/test_digestauth2.c
@@ -1366,7 +1366,7 @@ testDigestAuth (void)
     if (test_bind_uri)
       dauth_nonce_bind |= MHD_DAUTH_BIND_NONCE_URI_PARAMS;
 
-    d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+    d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                           port, NULL, NULL,
                           &ahc_echo, &rq_tr,
                           MHD_OPTION_DIGEST_AUTH_RANDOM_COPY,
diff --git a/src/testcurl/test_digestauth_emu_ext.c b/src/testcurl/test_digestauth_emu_ext.c
index 7a6e8e7b..8506a567 100644
--- a/src/testcurl/test_digestauth_emu_ext.c
+++ b/src/testcurl/test_digestauth_emu_ext.c
@@ -820,7 +820,7 @@ testDigestAuthEmu (void)
   else
     port = 4210;
 
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL,
                         &ahc_echo, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_get.c b/src/testcurl/test_get.c
index b44c8370..812aa840 100644
--- a/src/testcurl/test_get.c
+++ b/src/testcurl/test_get.c
@@ -394,7 +394,7 @@ testMultithreadedPoolGet (uint32_t poll_flag)
 
 
 static unsigned int
-testExternalGet (void)
+testExternalGet (int thread_unsafe)
 {
   struct MHD_Daemon *d;
   CURL *c;
@@ -424,7 +424,8 @@ testExternalGet (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG
+                        | (thread_unsafe ? MHD_USE_NO_THREAD_SAFETY : 0),
                         global_port, NULL, NULL,
                         &ahc_echo, NULL,
                         MHD_OPTION_URI_LOG_CALLBACK, &log_cb, NULL,
@@ -890,14 +891,20 @@ main (int argc, char *const *argv)
   if (0 != curl_global_init (CURL_GLOBAL_WIN32))
     return 2;
   global_port = 0;
-  test_result = testExternalGet ();
+  test_result = testExternalGet (! 0);
   if (test_result)
-    fprintf (stderr, "FAILED: testExternalGet () - %u.\n", test_result);
+    fprintf (stderr, "FAILED: testExternalGet (!0) - %u.\n", test_result);
   else if (verbose)
     printf ("PASSED: testExternalGet ().\n");
   errorCount += test_result;
   if (MHD_YES == MHD_is_feature_supported (MHD_FEATURE_THREADS))
   {
+    test_result += testExternalGet (0);
+    if (test_result)
+      fprintf (stderr, "FAILED: testExternalGet (0) - %u.\n", test_result);
+    else if (verbose)
+      printf ("PASSED: testExternalGet ().\n");
+    errorCount += test_result;
     test_result += testInternalGet (0);
     if (test_result)
       fprintf (stderr, "FAILED: testInternalGet (0) - %u.\n", test_result);
diff --git a/src/testcurl/test_get_chunked.c b/src/testcurl/test_get_chunked.c
index 1b985ce2..9ffa8041 100644
--- a/src/testcurl/test_get_chunked.c
+++ b/src/testcurl/test_get_chunked.c
@@ -591,7 +591,7 @@ testExternalGet (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
                         MHD_OPTION_END);
diff --git a/src/testcurl/test_get_close_keep_alive.c b/src/testcurl/test_get_close_keep_alive.c
index 5771bec9..b84e9640 100644
--- a/src/testcurl/test_get_close_keep_alive.c
+++ b/src/testcurl/test_get_close_keep_alive.c
@@ -958,7 +958,7 @@ startTestMhdDaemon (enum testMhdThreadsType thrType,
 
   if (testMhdThreadExternal == thrType)
     d = MHD_start_daemon (((unsigned int) thrType) | ((unsigned int) pollType)
-                          | MHD_USE_ERROR_LOG,
+                          | MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                           *pport, NULL, NULL,
                           &ahc_echo, NULL,
                           MHD_OPTION_URI_LOG_CALLBACK, &log_cb, NULL,
diff --git a/src/testcurl/test_get_iovec.c b/src/testcurl/test_get_iovec.c
index 00e4fa3e..f1a83ece 100644
--- a/src/testcurl/test_get_iovec.c
+++ b/src/testcurl/test_get_iovec.c
@@ -481,7 +481,7 @@ testMultithreadedPoolGet (void)
 
 
 static unsigned int
-testExternalGet (void)
+testExternalGet (int thread_unsafe)
 {
   struct MHD_Daemon *d;
   CURL *c;
@@ -516,7 +516,8 @@ testExternalGet (void)
   cbc.buf = (char *) readbuf;
   cbc.size = sizeof(readbuf);
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG
+                        | (thread_unsafe ? MHD_USE_NO_THREAD_SAFETY : 0),
                         port, NULL, NULL, &ahc_cont, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
                         MHD_OPTION_END);
@@ -773,8 +774,9 @@ main (int argc, char *const *argv)
     errorCount += testMultithreadedGet ();
     errorCount += testMultithreadedPoolGet ();
     errorCount += testUnknownPortGet ();
+    errorCount += testExternalGet (0);
   }
-  errorCount += testExternalGet ();
+  errorCount += testExternalGet (! 0);
   if (errorCount != 0)
     fprintf (stderr, "Error (code: %u)\n", errorCount);
   curl_global_cleanup ();
diff --git a/src/testcurl/test_get_sendfile.c b/src/testcurl/test_get_sendfile.c
index 698a7c2e..01be8122 100644
--- a/src/testcurl/test_get_sendfile.c
+++ b/src/testcurl/test_get_sendfile.c
@@ -337,7 +337,7 @@ testMultithreadedPoolGet (void)
 
 
 static unsigned int
-testExternalGet (void)
+testExternalGet (int thread_unsafe)
 {
   struct MHD_Daemon *d;
   CURL *c;
@@ -373,7 +373,8 @@ testExternalGet (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG
+                        | (thread_unsafe ? MHD_USE_NO_THREAD_SAFETY : 0),
                         port, NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
                         MHD_OPTION_END);
@@ -660,8 +661,9 @@ main (int argc, char *const *argv)
     errorCount += testMultithreadedGet ();
     errorCount += testMultithreadedPoolGet ();
     errorCount += testUnknownPortGet ();
+    errorCount += testExternalGet (0);
   }
-  errorCount += testExternalGet ();
+  errorCount += testExternalGet (! 0);
   if (errorCount != 0)
     fprintf (stderr, "Error (code: %u)\n", errorCount);
   curl_global_cleanup ();
diff --git a/src/testcurl/test_head.c b/src/testcurl/test_head.c
index 4f820880..226663d3 100644
--- a/src/testcurl/test_head.c
+++ b/src/testcurl/test_head.c
@@ -756,7 +756,7 @@ testHead (void)
   else
     port = 4220 + oneone ? 0 : 1;
 
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL,
                         &ahcCheck, &ahc_param,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_large_put.c b/src/testcurl/test_large_put.c
index d2612fa8..64669a44 100644
--- a/src/testcurl/test_large_put.c
+++ b/src/testcurl/test_large_put.c
@@ -647,7 +647,7 @@ testPutExternal (void)
   cbc.size = 2048;
   cbc.pos = 0;
   multi = NULL;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port,
                         NULL, NULL, &ahc_echo, &done_flag,
                         MHD_OPTION_CONNECTION_MEMORY_LIMIT,
diff --git a/src/testcurl/test_parse_cookies.c b/src/testcurl/test_parse_cookies.c
index d81f0765..41c408a9 100644
--- a/src/testcurl/test_parse_cookies.c
+++ b/src/testcurl/test_parse_cookies.c
@@ -1646,7 +1646,7 @@ testExternalPolling (void)
   else
     port = 1340 + oneone ? 0 : 6 + (uint16_t) (1 + discp_level);
 
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL,
                         &ahcCheck, &ahc_param,
                         MHD_OPTION_CLIENT_DISCIPLINE_LVL,
diff --git a/src/testcurl/test_patch.c b/src/testcurl/test_patch.c
index e5f37901..c13712e0 100644
--- a/src/testcurl/test_patch.c
+++ b/src/testcurl/test_patch.c
@@ -374,7 +374,7 @@ testExternalPut (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port,
                         NULL, NULL, &ahc_echo, &done_flag,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_post.c b/src/testcurl/test_post.c
index 3f64c0a4..58409cc1 100644
--- a/src/testcurl/test_post.c
+++ b/src/testcurl/test_post.c
@@ -433,7 +433,7 @@ testExternalPost (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_NOTIFY_COMPLETED, &completed_cb, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_post_loop.c b/src/testcurl/test_post_loop.c
index 7144abdd..5f2b7ad3 100644
--- a/src/testcurl/test_post_loop.c
+++ b/src/testcurl/test_post_loop.c
@@ -431,7 +431,7 @@ testExternalPost (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
                         MHD_OPTION_END);
diff --git a/src/testcurl/test_postform.c b/src/testcurl/test_postform.c
index bbd0d137..32809fa9 100644
--- a/src/testcurl/test_postform.c
+++ b/src/testcurl/test_postform.c
@@ -557,7 +557,7 @@ testExternalPost (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_NOTIFY_COMPLETED, &completed_cb, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_process_arguments.c b/src/testcurl/test_process_arguments.c
index f9720b89..8f010057 100644
--- a/src/testcurl/test_process_arguments.c
+++ b/src/testcurl/test_process_arguments.c
@@ -149,7 +149,7 @@ testExternalGet (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
                         MHD_OPTION_END);
diff --git a/src/testcurl/test_process_headers.c b/src/testcurl/test_process_headers.c
index ce30b8a9..34f52d5a 100644
--- a/src/testcurl/test_process_headers.c
+++ b/src/testcurl/test_process_headers.c
@@ -406,7 +406,7 @@ testExternalGet (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL, &ahc_echo, NULL,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
                         MHD_OPTION_END);
diff --git a/src/testcurl/test_put.c b/src/testcurl/test_put.c
index 97ed8591..e321a0b4 100644
--- a/src/testcurl/test_put.c
+++ b/src/testcurl/test_put.c
@@ -398,7 +398,7 @@ testExternalPut (void)
   cbc.buf = buf;
   cbc.size = 2048;
   cbc.pos = 0;
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port,
                         NULL, NULL, &ahc_echo, &done_flag,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_put_broken_len.c b/src/testcurl/test_put_broken_len.c
index 65e8cd82..52a48c79 100644
--- a/src/testcurl/test_put_broken_len.c
+++ b/src/testcurl/test_put_broken_len.c
@@ -628,7 +628,7 @@ performTest (void)
   else
     port = 4220 + oneone ? 0 : 1;
 
-  d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+  d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                         port, NULL, NULL,
                         &ahcCheck, &ahc_param,
                         MHD_OPTION_APP_FD_SETSIZE, (int) FD_SETSIZE,
diff --git a/src/testcurl/test_put_header_fold.c b/src/testcurl/test_put_header_fold.c
index 9b77ed99..ad9b7450 100644
--- a/src/testcurl/test_put_header_fold.c
+++ b/src/testcurl/test_put_header_fold.c
@@ -1147,7 +1147,7 @@ performCheck (void)
       mem_limit = (size_t) ((TEST_UPLOAD_DATA_SIZE * 4) / 3 + 2
                             + HEADERS_POINTERS_SIZE);
 
-    d = MHD_start_daemon (MHD_USE_ERROR_LOG,
+    d = MHD_start_daemon (MHD_USE_ERROR_LOG | MHD_USE_NO_THREAD_SAFETY,
                           port, NULL, NULL,
                           &ahcCheck, &ahc_param,
                           MHD_OPTION_CONNECTION_MEMORY_LIMIT, mem_limit,
diff --git a/src/testcurl/test_toolarge.c b/src/testcurl/test_toolarge.c
index e5d519c3..414f5c4f 100644
--- a/src/testcurl/test_toolarge.c
+++ b/src/testcurl/test_toolarge.c
@@ -1453,7 +1453,8 @@ startTestMhdDaemon (enum testMhdThreadsType thrType,
 
   if (testMhdThreadExternal == thrType)
     d = MHD_start_daemon (((unsigned int) thrType) | ((unsigned int) pollType)
-                          | (verbose ? MHD_USE_ERROR_LOG : 0),
+                          | (verbose ? MHD_USE_ERROR_LOG : 0)
+                          | MHD_USE_NO_THREAD_SAFETY,
                           *pport, NULL, NULL,
                           &ahcCheck, *ahc_param,
                           MHD_OPTION_URI_LOG_CALLBACK, &check_uri_cb,
diff --git a/src/testcurl/test_tricky.c b/src/testcurl/test_tricky.c
index b3f52484..8cb53a80 100644
--- a/src/testcurl/test_tricky.c
+++ b/src/testcurl/test_tricky.c
@@ -964,7 +964,8 @@ startTestMhdDaemon (enum testMhdThreadsType thrType,
 
   if (testMhdThreadExternal == thrType)
     d = MHD_start_daemon (((unsigned int) thrType) | ((unsigned int) pollType)
-                          | (verbose ? MHD_USE_ERROR_LOG : 0),
+                          | (verbose ? MHD_USE_ERROR_LOG : 0)
+                          | MHD_USE_NO_THREAD_SAFETY,
                           *pport, NULL, NULL,
                           &ahcCheck, *ahc_param,
                           MHD_OPTION_URI_LOG_CALLBACK, &check_uri_cb,
diff --git a/src/testzzuf/test_get.c b/src/testzzuf/test_get.c
index c1a245d6..a687555a 100644
--- a/src/testzzuf/test_get.c
+++ b/src/testzzuf/test_get.c
@@ -1272,9 +1272,12 @@ print_test_starting (unsigned int daemon_flags)
   else
   {
     if (0 != (MHD_USE_EPOLL & daemon_flags))
-      printf ("\nStarting test with external polling and internal 'epoll'.\n");
+      printf ("\nStarting test with%s thread safety with external polling "
+              "and internal 'epoll'.\n",
+              ((0 != (MHD_USE_NO_THREAD_SAFETY & daemon_flags)) ? "out" : ""));
     else
-      printf ("\nStarting test with external polling.\n");
+      printf ("\nStarting test with%s thread safety with external polling.\n",
+              ((0 != (MHD_USE_NO_THREAD_SAFETY & daemon_flags)) ? "out" : ""));
   }
   fflush (stdout);
 }
@@ -1623,8 +1626,9 @@ run_all_checks (void)
       if ((77 == testRes) || (99 == testRes))
         return testRes;
     }
+    testRes = testExternalPolling (&port, MHD_NO_FLAG);
   }
-  testRes = testExternalPolling (&port, MHD_NO_FLAG);
+  testRes = testExternalPolling (&port, MHD_USE_NO_THREAD_SAFETY);
   if ((77 == testRes) || (99 == testRes))
     return testRes;
   ret += testRes;