diff --git a/install/dist/lib/centos52.lib.php b/install/dist/lib/centos52.lib.php
index 7f8901b1af3d5def8bb649ef8d62c8411a2abdf3..7d9b78caa55758375ab6b051514602971f24ae8a 100644
--- a/install/dist/lib/centos52.lib.php
+++ b/install/dist/lib/centos52.lib.php
@@ -144,7 +144,7 @@ class installer extends installer_dist {
 		if(is_file($conf['postfix']['config_dir'].'/master.cf')) copy($conf['postfix']['config_dir'].'/master.cf', $conf['postfix']['config_dir'].'/master.cf~');
 		$content = rf($conf['postfix']['config_dir'].'/master.cf');
 		// Only add the content if we had not addded it before
-		if(!preg_match('/^amavis\s+/m', $content)) {
+		if(!preg_match('/^amavis\s+unix\s+/m', $content)) {
 			unset($content);
 			$content = rfsel($conf['ispconfig_install_dir'].'/server/conf-custom/install/master_cf_amavis.master', 'tpl/master_cf_amavis.master');
 			af($conf['postfix']['config_dir'].'/master.cf', $content);
diff --git a/install/dist/lib/centos53.lib.php b/install/dist/lib/centos53.lib.php
index ee586f78d5332ec62a4e47abce56b215f7d2aa84..c7e11e50a3ddb4bed6befeeb9e335ca7e3bd1bb8 100644
--- a/install/dist/lib/centos53.lib.php
+++ b/install/dist/lib/centos53.lib.php
@@ -145,7 +145,7 @@ class installer extends installer_dist {
 		if(is_file($conf['postfix']['config_dir'].'/master.cf')) copy($conf['postfix']['config_dir'].'/master.cf', $conf['postfix']['config_dir'].'/master.cf~');
 		$content = rf($conf['postfix']['config_dir'].'/master.cf');
 		// Only add the content if we had not addded it before
-		if(!preg_match('/^amavis\s+/m', $content)) {
+		if(!preg_match('/^amavis\s+unix\s+/m', $content)) {
 			unset($content);
 			$content = rfsel($conf['ispconfig_install_dir'].'/server/conf-custom/install/master_cf_amavis.master', 'tpl/master_cf_amavis.master');
 			af($conf['postfix']['config_dir'].'/master.cf', $content);
diff --git a/install/dist/lib/fedora.lib.php b/install/dist/lib/fedora.lib.php
index bbcdfa68fa4cea5f7d568a81d8302b579de00032..f5c04ad9fd5ea43da9da373b234edfbd792d3f78 100644
--- a/install/dist/lib/fedora.lib.php
+++ b/install/dist/lib/fedora.lib.php
@@ -500,7 +500,7 @@ class installer_dist extends installer_base {
 		if(is_file($conf['postfix']['config_dir'].'/master.cf')) copy($conf['postfix']['config_dir'].'/master.cf', $conf['postfix']['config_dir'].'/master.cf~');
 		$content = rf($conf['postfix']['config_dir'].'/master.cf');
 		// Only add the content if we had not addded it before
-		if(!preg_match('/^amavis\s+/m', $content)) {
+		if(!preg_match('/^amavis\s+unix\s+/m', $content)) {
 			unset($content);
 			$content = rfsel($conf['ispconfig_install_dir'].'/server/conf-custom/install/master_cf_amavis.master', 'tpl/master_cf_amavis.master');
 			af($conf['postfix']['config_dir'].'/master.cf', $content);
diff --git a/install/dist/lib/gentoo.lib.php b/install/dist/lib/gentoo.lib.php
index e7aac8c61fb9c9612bc331427f800d634f7e243b..40f552c66228f8ecfb951efb55c272381e3ceaef 100644
--- a/install/dist/lib/gentoo.lib.php
+++ b/install/dist/lib/gentoo.lib.php
@@ -335,7 +335,7 @@ class installer extends installer_base
         // Append the configuration for amavisd to the master.cf file
 		$content = rf($conf['postfix']['config_dir'].'/master.cf');
 		// Only add the content if we had not addded it before
-		if(!preg_match('/^amavis\s+/m', $content)) {
+		if(!preg_match('/^amavis\s+unix\s+/m', $content)) {
 			unset($content);
 			$content = $this->get_template_file('master_cf_amavis', true);
 			af($conf['postfix']['config_dir'].'/master.cf', $content);
diff --git a/install/dist/lib/opensuse.lib.php b/install/dist/lib/opensuse.lib.php
index a052615e43f3366052e55898b9d78516a0e04520..1c47271b422e1f8659d66fb31b155abc4f98fb3a 100644
--- a/install/dist/lib/opensuse.lib.php
+++ b/install/dist/lib/opensuse.lib.php
@@ -534,7 +534,7 @@ class installer_dist extends installer_base {
 		if(is_file($conf["postfix"]["config_dir"].'/master.cf')) copy($conf["postfix"]["config_dir"].'/master.cf', $conf["postfix"]["config_dir"].'/master.cf~');
 		$content = rf($conf["postfix"]["config_dir"].'/master.cf');
         // Only add the content if we had not addded it before
-		if(!preg_match('/^amavis\s+/m', $content)) {
+		if(!preg_match('/^amavis\s+unix\s+/m', $content)) {
 			unset($content);
 			$content = rfsel($conf['ispconfig_install_dir'].'/server/conf-custom/install/master_cf_amavis.master', 'tpl/master_cf_amavis.master');
 			af($conf['postfix']['config_dir'].'/master.cf', $content);