diff --git a/api/src/Vfs.php b/api/src/Vfs.php
index a2359cb400..deda97ed11 100644
--- a/api/src/Vfs.php
+++ b/api/src/Vfs.php
@@ -1504,6 +1504,11 @@ class Vfs extends Vfs\Base
 
 		//error_log("Total files: " . $total_files . " Peak memory to zip: " . self::hsize(memory_get_peak_usage(true)));
 
+		// FIRST: switch off zlib.output_compression, as this would limit downloads in size to memory_limit
+		ini_set('zlib.output_compression',0);
+		// SECOND: end all active output buffering
+		while(ob_end_clean()) {}
+
 		// Stream the file to the client
 		header("Content-Type: application/zip");
 		header("Content-Length: " . filesize($zip_file));
diff --git a/importexport/inc/class.importexport_export_ui.inc.php b/importexport/inc/class.importexport_export_ui.inc.php
index 61192d66af..aa99a70f8b 100644
--- a/importexport/inc/class.importexport_export_ui.inc.php
+++ b/importexport/inc/class.importexport_export_ui.inc.php
@@ -446,6 +446,11 @@ class importexport_export_ui {
 		$appname = $_GET['_appname'];
 		$nicefname = $_GET['filename'] ? $_GET['filename'] : 'egw_export_'.$appname.'-'.date('Y-m-d');
 
+		// FIRST: switch off zlib.output_compression, as this would limit downloads in size to memory_limit
+		ini_set('zlib.output_compression',0);
+		// SECOND: end all active output buffering
+		while(ob_end_clean()) {}
+
 		// Get charset
 		$charset = Api\Cache::getSession('importexport', $tmpfname);
 
diff --git a/setup/db_backup.php b/setup/db_backup.php
index c98f29b90b..f6eca27aef 100644
--- a/setup/db_backup.php
+++ b/setup/db_backup.php
@@ -42,8 +42,12 @@ if (!empty($_POST['download']))
 {
 	$file = key($_POST['download']);
 	$file = $db_backup->backup_dir.'/'.basename($file);	// basename to now allow to change the dir
-	while (@ob_end_clean()) {}      // end all active output buffering
-	ini_set('zlib.output_compression',0);   // switch off zlib.output_compression, as this would limit downloads in size to memory_limit
+
+	// FIRST: switch off zlib.output_compression, as this would limit downloads in size to memory_limit
+	ini_set('zlib.output_compression',0);
+	// SECOND: end all active output buffering
+	while(ob_end_clean()) {}
+
 	Api\Header\Content::type(basename($file));
 	readfile($file);
 	exit;
@@ -310,4 +314,4 @@ if ($run_in_egw)
 else
 {
 	$GLOBALS['egw_setup']->html->show_footer();
-}
+}
\ No newline at end of file