diff --git a/phpBB/phpbb/log/log.php b/phpBB/phpbb/log/log.php
index 3d995b4e4a..d46e3d1f3f 100644
--- a/phpBB/phpbb/log/log.php
+++ b/phpBB/phpbb/log/log.php
@@ -229,8 +229,8 @@ class log implements \phpbb\log\log_interface
 		}
 
 		$sql_ary = array(
-			'user_id'		=> $user_id,
-			'log_ip'		=> $log_ip,
+			'user_id'		=> !empty($user_id) ? $user_id : ANONYMOUS,
+			'log_ip'		=> !empty($log_ip) ? $log_ip : '',
 			'log_time'		=> $log_time,
 			'log_operation'	=> $log_operation,
 		);
diff --git a/tests/log/add_test.php b/tests/log/add_test.php
index bacc0c76f7..29d3adaeb6 100644
--- a/tests/log/add_test.php
+++ b/tests/log/add_test.php
@@ -88,5 +88,14 @@ class phpbb_log_add_test extends phpbb_database_test_case
 
 		// Invalid mode specified
 		$this->assertFalse($log->add('mode_does_not_exist', $user_id, $log_ip, $log_operation, $log_time));
+
+		// null user and null ip given
+		$this->assertEquals(3, $log->add($mode, null, null, $log_operation, $log_time), 'Adding log with null user_id and null user_ip failed');
+		$sql = 'SELECT user_id, log_ip FROM ' . LOG_TABLE . ' WHERE log_id = 3';
+		$result = $db->sql_query($sql);
+		$row = $db->sql_fetchrow($result);
+		$db->sql_freeresult($result);
+		$this->assertEquals(ANONYMOUS, $row['user_id'], 'Adding log with null user_id failed');
+		$this->assertEquals('', $row['log_ip'], 'Adding log with null user_ip failed');
 	}
 }