diff --git a/tests/data/Makefile.am b/tests/data/Makefile.am
index 5063e0210f..db1f86e356 100644
--- a/tests/data/Makefile.am
+++ b/tests/data/Makefile.am
@@ -109,7 +109,7 @@ test727 test728 test729 test730 test731 test732 test733 test734 test735 \
test736 test737 test738 test739 test740 test741 test742 test743 test744 \
test745 test746 test747 test748 test749 test750 test751 test752 test753 \
test754 test755 test756 test757 test758 test759 test760 test761 test762 \
-test763 test764 test765 \
+test763 test764 test765 test766 \
\
test780 test781 test782 test783 test784 test785 test786 test787 test788 \
test789 test790 test791 test792 test793 test794 test796 test797 \
diff --git a/tests/data/test766 b/tests/data/test766
new file mode 100644
index 0000000000..6beb341810
--- /dev/null
+++ b/tests/data/test766
@@ -0,0 +1,54 @@
+
+
+
+FTP
+PORT
+CURLOPT_SOCKOPTFUNCTION
+
+
+
+# Server-side
+
+
+hello
+
+
+
+# Client-side
+
+
+ftp
+
+
+lib%TESTNUMBER
+
+
+FTP PORT with sockopt callback refusing the accept
+
+
+ftp://%HOSTIP:%FTPPORT/path/%TESTNUMBER
+
+
+
+# Verify data after the test has been "shot"
+
+# Strip off parts of the PORT and EPRT commands that might differ
+
+s/^PORT (.*)/PORT/
+s/^EPRT \|1\|(.*)/EPRT \|1\|/
+
+
+USER anonymous
+PASS ftp@example.com
+PWD
+CWD path
+EPRT |1|
+
+
+# 42 == CURLE_ABORTED_BY_CALLBACK
+
+42
+
+
+
+
diff --git a/tests/libtest/Makefile.inc b/tests/libtest/Makefile.inc
index d8735a44e1..cac833f26f 100644
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@@ -76,6 +76,7 @@ TESTS_C = \
lib694.c lib695.c \
lib751.c lib753.c lib758.c \
lib757.c \
+ lib766.c \
lib1156.c \
lib1301.c lib1308.c \
lib1485.c \
diff --git a/tests/libtest/lib766.c b/tests/libtest/lib766.c
new file mode 100644
index 0000000000..4a64c3e0a2
--- /dev/null
+++ b/tests/libtest/lib766.c
@@ -0,0 +1,127 @@
+/***************************************************************************
+ * _ _ ____ _
+ * Project ___| | | | _ \| |
+ * / __| | | | |_) | |
+ * | (__| |_| | _ <| |___
+ * \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, , et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+
+#include "first.h"
+
+#include "memdebug.h"
+
+static int sockopt_766(void *clientp,
+ curl_socket_t curlfd,
+ curlsocktype purpose)
+{
+ (void)clientp;
+ (void)curlfd;
+ if(purpose == CURLSOCKTYPE_ACCEPT) {
+ curl_mfprintf(stderr,
+ "Return error from CURLOPT_SOCKOPTFUNCTION callback\n");
+ return 1; /* force error */
+ }
+ return 0;
+}
+
+static CURLcode test_lib766(const char *URL)
+{
+ CURL *easy = NULL;
+ CURLM *multi = NULL;
+ CURLcode res = CURLE_OK;
+ int running;
+ int msgs_left;
+ CURLMsg *msg;
+
+ start_test_timing();
+
+ res_global_init(CURL_GLOBAL_ALL);
+ if(res) {
+ return res;
+ }
+
+ easy_init(easy);
+ easy_setopt(easy, CURLOPT_VERBOSE, 1L);
+ easy_setopt(easy, CURLOPT_URL, URL);
+ easy_setopt(easy, CURLOPT_FTPPORT, "-");
+ easy_setopt(easy, CURLOPT_SOCKOPTFUNCTION, sockopt_766);
+
+ multi_init(multi);
+
+ multi_add_handle(multi, easy);
+
+ for(;;) {
+ struct timeval interval;
+ fd_set fdread;
+ fd_set fdwrite;
+ fd_set fdexcep;
+ long timeout = -99;
+ int maxfd = -99;
+
+ multi_perform(multi, &running);
+
+ abort_on_test_timeout();
+
+ if(!running)
+ break; /* done */
+
+ FD_ZERO(&fdread);
+ FD_ZERO(&fdwrite);
+ FD_ZERO(&fdexcep);
+
+ multi_fdset(multi, &fdread, &fdwrite, &fdexcep, &maxfd);
+
+ /* At this point, maxfd is guaranteed to be greater or equal than -1. */
+
+ multi_timeout(multi, &timeout);
+
+ /* At this point, timeout is guaranteed to be greater or equal than -1. */
+
+ if(timeout != -1L) {
+ int itimeout;
+#if LONG_MAX > INT_MAX
+ itimeout = (timeout > (long)INT_MAX) ? INT_MAX : (int)timeout;
+#else
+ itimeout = (int)timeout;
+#endif
+ interval.tv_sec = itimeout/1000;
+ interval.tv_usec = (itimeout%1000)*1000;
+ }
+ else {
+ interval.tv_sec = 0;
+ interval.tv_usec = 100000L; /* 100 ms */
+ }
+
+ select_test(maxfd + 1, &fdread, &fdwrite, &fdexcep, &interval);
+
+ abort_on_test_timeout();
+ }
+
+ msg = curl_multi_info_read(multi, &msgs_left);
+ if(msg)
+ res = msg->data.result;
+
+test_cleanup:
+
+ curl_multi_cleanup(multi);
+ curl_easy_cleanup(easy);
+ curl_global_cleanup();
+
+ return res;
+}