diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 5daa0e72270..d9fa9bc0bef 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -5900,6 +5900,7 @@ void do_connect(struct st_command *command)
   my_bool con_ssl= 0, con_compress= 0;
   my_bool con_pipe= 0;
   my_bool con_shm __attribute__ ((unused))= 0;
+  int connect_timeout= 0;
   struct st_connection* con_slot;
 
   static DYNAMIC_STRING ds_connection_name;
@@ -5996,6 +5997,9 @@ void do_connect(struct st_command *command)
       con_pipe= 1;
     else if (length == 3 && !strncmp(con_options, "SHM", 3))
       con_shm= 1;
+    else if (strncasecmp(con_options, "connect_timeout=",
+                         sizeof("connect_timeout=")-1) == 0)
+      connect_timeout= atoi(con_options + sizeof("connect_timeout=")-1);
     else
       die("Illegal option to connect: %.*s", 
           (int) (end - con_options), con_options);
@@ -6066,6 +6070,10 @@ void do_connect(struct st_command *command)
   if (opt_protocol)
     mysql_options(con_slot->mysql, MYSQL_OPT_PROTOCOL, (char*) &opt_protocol);
 
+  if (connect_timeout)
+    mysql_options(con_slot->mysql, MYSQL_OPT_CONNECT_TIMEOUT,
+                  (char*)&connect_timeout);
+
 #ifdef HAVE_SMEM
   if (con_shm)
   {
diff --git a/mysql-test/r/pool_of_threads.result b/mysql-test/r/pool_of_threads.result
index 7acb45121d6..f153ebc48f4 100644
--- a/mysql-test/r/pool_of_threads.result
+++ b/mysql-test/r/pool_of_threads.result
@@ -2157,23 +2157,22 @@ Warnings:
 Warning	1052	Column 'kundentyp' in group statement is ambiguous
 drop table t1;
 SET optimizer_switch=@save_optimizer_switch;
-SELECT sleep(5);
-SELECT sleep(5);
+SELECT sleep(50);
+SELECT sleep(50);
 # -- Success: more than --thread_pool_max_threads normal connections not possible
-sleep(5)
-0
-sleep(5)
-0
-SELECT sleep(5);
-SELECT sleep(5);
 SELECT 'Connection on extra port ok';
 Connection on extra port ok
 Connection on extra port ok
+SELECT sleep(5.5);
 SELECT 'Connection on extra port 2 ok';
 Connection on extra port 2 ok
 Connection on extra port 2 ok
 # -- Success: more than --extra-max-connections + 1 normal connections not possible
-sleep(5)
-0
-sleep(5)
+KILL QUERY <default_connection_ID>;
+KILL QUERY <con2_connection_ID>;
+sleep(50)
+1
+sleep(50)
+1
+sleep(5.5)
 0
diff --git a/mysql-test/t/pool_of_threads.cnf b/mysql-test/t/pool_of_threads.cnf
index c03e1da6450..f6651c878de 100644
--- a/mysql-test/t/pool_of_threads.cnf
+++ b/mysql-test/t/pool_of_threads.cnf
@@ -7,8 +7,5 @@ loose-thread_pool_max_threads= 2
 extra-port=        @ENV.MASTER_EXTRA_PORT
 extra-max-connections=1
 
-[client]
-connect-timeout=  2 
-
 [ENV]
 MASTER_EXTRA_PORT= @OPT.port
diff --git a/mysql-test/t/pool_of_threads.test b/mysql-test/t/pool_of_threads.test
index 4600128ff43..f13a096985c 100644
--- a/mysql-test/t/pool_of_threads.test
+++ b/mysql-test/t/pool_of_threads.test
@@ -15,20 +15,26 @@ SET optimizer_switch=@save_optimizer_switch;
 # connections on the extra port.
 
 # First set two connections running, and check that extra connection
-# on normal port fails due to--thread-pool-max_threads=2
+# on normal port fails due to --thread-pool-max-threads=2.
+# We can afford using a really long sleep, because we won't wait
+# till it ends, we'll interrupt it as soon as we don't need it anymore
+
 connection default;
-send SELECT sleep(5);
+--let $con1_id= `SELECT CONNECTION_ID()`
+
+send SELECT sleep(50);
 --sleep  1 
 
 connect(con2,localhost,root,,);
-connection con2;
-send SELECT sleep(5);
+--let $con2_id= `SELECT CONNECTION_ID()`
+
+send SELECT sleep(50);
 --sleep  0.5
 
 --disable_abort_on_error
 --disable_result_log
 --disable_query_log
-connect(con3,localhost,root,,);
+connect(con3,localhost,root,,,,,connect_timeout=2);
 --enable_query_log
 --enable_result_log
 --enable_abort_on_error
@@ -42,24 +48,15 @@ if ($error)
   --echo # -- Success: more than --thread_pool_max_threads normal connections not possible
 }
 
-connection default;
---reap
-connection con2;
---reap
-
-# Now try again, but this time use the extra port to successfully connect.
-
-connection default;
-send SELECT sleep(5);
-
-connection con2;
-send SELECT sleep(5);
---sleep 1
-
 connect(extracon,127.0.0.1,root,,test,$MASTER_EXTRA_PORT,);
 connection extracon;
 SELECT 'Connection on extra port ok';
 
+# Here, sleep just for slightly longer than 5 sec to trigger MDEV-4566
+# (abort in interruptible wait connection check).
+send SELECT sleep(5.5);
+
+
 connect(extracon2,127.0.0.1,root,,test,$MASTER_EXTRA_PORT,);
 connection extracon2;
 SELECT 'Connection on extra port 2 ok';
@@ -67,7 +64,7 @@ SELECT 'Connection on extra port 2 ok';
 --disable_abort_on_error
 --disable_result_log
 --disable_query_log
-connect(extracon3,127.0.0.1,root,,test,$MASTER_EXTRA_PORT,);
+connect(extracon3,127.0.0.1,root,,test,$MASTER_EXTRA_PORT,,connect_timeout=2);
 --enable_query_log
 --enable_result_log
 --enable_abort_on_error
@@ -81,7 +78,16 @@ if ($error)
   --echo # -- Success: more than --extra-max-connections + 1 normal connections not possible
 }
 
+connection extracon2;
+--replace_result $con1_id <default_connection_ID>
+eval KILL QUERY $con1_id;
+--replace_result $con2_id <con2_connection_ID>
+eval KILL QUERY $con2_id;
+
 connection default;
 --reap
 connection con2;
 --reap
+
+connection extracon;
+--reap