diff --git a/Dockerfile b/Dockerfile
index a52759e..506c28a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,10 +1,13 @@
 ARG PHP_IMAGE=php:8.0
 FROM $PHP_IMAGE
 
+RUN docker-php-ext-configure pcntl --enable-pcntl \
+    && docker-php-ext-install -j$(nproc) pcntl
+
 RUN apt-get update && apt-get install -y \ 
 	git \
 	zlib1g-dev \
-	memcached ; 
+	memcached ;
 
 COPY docker/host.conf /etc/host.conf
 
diff --git a/README b/README
index b36fa46..07f8f89 100644
--- a/README
+++ b/README
@@ -3,7 +3,7 @@ This is an official repository for pecl-memcache plugin since 2019.
 This repository contains modified pecl-memcache plugin ported to PHP8,
 which was originally developed for the need of hosting company in Slovakia (Websupport.sk). 
 
-The latest release is 8.0 (released: 2020-12-06) with support for PHP 8.0.
+The latest release is 8.0 (released: 2020-12-06) with support for PHP 8.0 and unofficial support for PHP 7.3 and 7.4
 
 Please use version 4.0.5.1 (released: 2020-12-19) for PHP 7.x from branch NON_BLOCKING_IO_php7.
 
diff --git a/Vagrantfile b/Vagrantfile
new file mode 100644
index 0000000..8665890
--- /dev/null
+++ b/Vagrantfile
@@ -0,0 +1,17 @@
+# -*- mode: ruby -*-
+# vi: set ft=ruby :
+
+VAGRANTFILE_API_VERSION = '2'
+
+Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
+    config.vm.box = 'ubuntu/bionic64'
+
+    config.vm.provider :virtualbox do |vb|
+        vb.name = 'ext-memcache-dev'
+        vb.memory = 1024
+        vb.cpus = 2
+    end
+
+    config.vm.provision 'docker'
+
+end
diff --git a/src/memcache.c b/src/memcache.c
index 7c3a660..2cb675b 100644
--- a/src/memcache.c
+++ b/src/memcache.c
@@ -924,7 +924,7 @@ static void php_mmc_store(INTERNAL_FUNCTION_PARAMETERS, int op) /* {{{ */
 				continue;
 			}
 
-			/* begin sending requests immediatly */
+			/* begin sending requests immediately */
 			mmc_pool_select(pool);
 		} ZEND_HASH_FOREACH_END();
 	}
@@ -1089,7 +1089,7 @@ static void php_mmc_numeric(INTERNAL_FUNCTION_PARAMETERS, int deleted, int inver
 				continue;
 			}
 
-			/* begin sending requests immediatly */
+			/* begin sending requests immediately */
 			mmc_pool_select(pool);
 		} ZEND_HASH_FOREACH_END();
 
@@ -1319,8 +1319,9 @@ static void php_mmc_connect(INTERNAL_FUNCTION_PARAMETERS, zend_bool persistent)
 	size_t host_len;
 	zend_long tcp_port = MEMCACHE_G(default_port);
 	double timeout = MMC_DEFAULT_TIMEOUT;
+	zend_bool null_port;
 
-	if (zend_parse_parameters(ZEND_NUM_ARGS(), "s|ld", &host, &host_len, &tcp_port, &timeout) == FAILURE) {
+	if (zend_parse_parameters(ZEND_NUM_ARGS(), "s|l!d", &host, &host_len, &tcp_port, &null_port, &timeout) == FAILURE) {
 		return;
 	}
 
@@ -2492,7 +2493,7 @@ PHP_FUNCTION(memcache_flush)
 		pool->protocol->flush(request, delay);
 
 		if (mmc_pool_schedule(pool, pool->servers[i], request) == MMC_OK) {
-			/* begin sending requests immediatly */
+			/* begin sending requests immediately */
 			mmc_pool_select(pool);
 		}
 	}
diff --git a/src/memcache_pool.c b/src/memcache_pool.c
index 733a0c5..e52389d 100644
--- a/src/memcache_pool.c
+++ b/src/memcache_pool.c
@@ -1303,7 +1303,7 @@ int mmc_pool_schedule_get(
 		pool->protocol->end_get(mmc->buildreq);
 		mmc_pool_schedule(pool, mmc, mmc->buildreq);
 
-		/* begin sending requests immediatly */
+		/* begin sending requests immediately */
 		mmc_pool_select(pool);
 
 		mmc->buildreq = mmc_pool_request_get(
diff --git a/src/memcache_session.c b/src/memcache_session.c
index e4a80de..d3aab24 100644
--- a/src/memcache_session.c
+++ b/src/memcache_session.c
@@ -319,7 +319,7 @@ PS_READ_FUNC(memcache)
 			ZVAL_NULL(&addresult);
 
 			/* third request fetches the data, data is only valid if either of the lock requests succeeded */
-			ZVAL_EMPTY_STRING(&dataresult);
+			ZVAL_NULL(&dataresult);
 
 			/* create requests */
 			if (php_mmc_session_read_request(pool, &zkey, lockparam, &addresult, dataparam, &lockrequest, &addrequest, &datarequest) != MMC_OK) {
diff --git a/tests/redundancy_test.phpt b/tests/redundancy_test.phpt
new file mode 100644
index 0000000..fb5ab84
--- /dev/null
+++ b/tests/redundancy_test.phpt
@@ -0,0 +1,75 @@
+--TEST--
+redundancy test
+--SKIPIF--
+<?php include 'connect.inc'; if (!MEMCACHE_HAVE_SESSION) print 'skip not compiled with session support'; else if (!function_exists('pcntl_fork')) print 'skip not compiled with pcntl_fork() support'; ?>
+--FILE--
+<?php
+
+include 'connect.inc';
+
+$sid = md5(rand());
+
+ini_set('session.save_handler', 'memcache');
+ini_set('memcache.session_save_path', "tcp://$host:$port,tcp://$host2:$port2");
+ini_set('memcache.session_redundancy', 3);
+
+$memcache1 = test_connect1();
+$memcache2 = test_connect2();
+
+$pid = pcntl_fork();
+if (!$pid) {
+    // In child process
+    session_id($sid);
+    session_start();
+    if (!isset($_SESSION['counter']))
+        $_SESSION['counter'] = 0;
+    $_SESSION['counter'] += 1;
+    session_write_close();
+
+    exit(0);
+}
+pcntl_waitpid($pid, $status);
+
+$memcache1->flush();
+
+$pid = pcntl_fork();
+if (!$pid) {
+    // In child process
+    session_id($sid);
+    session_start();
+    if (!isset($_SESSION['counter']))
+        $_SESSION['counter'] = 0;
+    $_SESSION['counter'] += 1;
+    session_write_close();
+
+    exit(0);
+}
+pcntl_waitpid($pid, $status);
+
+$memcache2->flush();
+
+$pid = pcntl_fork();
+if (!$pid) {
+    // In child process
+    session_id($sid);
+    session_start();
+    if (!isset($_SESSION['counter']))
+        $_SESSION['counter'] = 0;
+    $_SESSION['counter'] += 1;
+    session_write_close();
+
+    exit(0);
+}
+pcntl_waitpid($pid, $status);
+
+
+session_id($sid);
+session_start();
+var_dump($_SESSION);
+
+?>
+--EXPECT--
+array(1) {
+  ["counter"]=>
+  int(3)
+}