diff --git a/phpgwapi/inc/class.accounts.inc.php b/phpgwapi/inc/class.accounts.inc.php
index 6be7823170..b42fa63504 100644
--- a/phpgwapi/inc/class.accounts.inc.php
+++ b/phpgwapi/inc/class.accounts.inc.php
@@ -563,7 +563,10 @@ class accounts
 				$this->set_memberships($memberships, $id);	// invalidates cache for account_id and primary group
 			}
 		}
-		self::cache_invalidate($data['account_id']);
+		// as some backends set (group-)members in save, we need to invalidate their members too!
+		$invalidate = isset($data['account_members']) ? $data['account_members'] : array();
+		$invalidate[] = $data['account_id'];
+		self::cache_invalidate($invalidate);
 
 		return $id;
 	}
diff --git a/phpgwapi/inc/class.vfs_home_hooks.inc.php b/phpgwapi/inc/class.vfs_home_hooks.inc.php
index a743942c80..184125376f 100644
--- a/phpgwapi/inc/class.vfs_home_hooks.inc.php
+++ b/phpgwapi/inc/class.vfs_home_hooks.inc.php
@@ -120,7 +120,7 @@ class vfs_home_hooks
 		if (egw_vfs::mkdir($dir='/home/'.$data['account_lid'],0070,0))
 		{
 			egw_vfs::chown($dir,0);
-			egw_vfs::chgrp($dir,$data['account_id']);
+			egw_vfs::chgrp($dir,abs($data['account_id']));	// gid in Vfs is positiv!
 			egw_vfs::chmod($dir,0070);	// only group has access
 		}
 		egw_vfs::$is_root = false;