diff --git a/phpBB/phpbb/install/module/update_filesystem/task/diff_files.php b/phpBB/phpbb/install/module/update_filesystem/task/diff_files.php
index 2f6048b4fd..40bc16b439 100644
--- a/phpBB/phpbb/install/module/update_filesystem/task/diff_files.php
+++ b/phpBB/phpbb/install/module/update_filesystem/task/diff_files.php
@@ -155,13 +155,47 @@ class diff_files extends task_base
 
 				$diff = new \diff3($file_contents[0], $file_contents[1], $file_contents[2]);
 
+				$file_is_merged = $diff->merged_output() === $file_contents[1];
+
 				// Handle conflicts
 				if ($diff->get_num_conflicts() !== 0)
 				{
+					// Check if current file content is merge of new or original file
+					$tmp = [
+						'file1'		=> $file_contents[1],
+						'file2'		=> implode("\n", $diff->merged_new_output()),
+					];
+
+					$diff2 = new \diff($tmp['file1'], $tmp['file2']);
+					$empty = $diff2->is_empty();
+
+					if (!$empty)
+					{
+						unset($tmp, $diff2);
+
+						// We check if the user merged with his output
+						$tmp = [
+							'file1'		=> $file_contents[1],
+							'file2'		=> implode("\n", $diff->merged_orig_output()),
+						];
+
+						$diff2 = new \diff($tmp['file1'], $tmp['file2']);
+						$empty = $diff2->is_empty();
+					}
+
+					unset($diff2);
+
+					if (!$empty && in_array($filename, $merge_conflicts))
+					{
 					$merge_conflicts[] = $filename;
 				}
+					else
+					{
+						$file_is_merged = true;
+					}
+				}
 
-				if ($diff->merged_output() !== $file_contents[1])
+				if (!$file_is_merged)
 				{
 					// Save merged output
 					$this->cache->put(
@@ -223,6 +257,7 @@ class diff_files extends task_base
 
 		$this->iohandler->finish_progress('ALL_FILES_DIFFED');
 		$this->installer_config->set('merge_conflict_list', $merge_conflicts);
+		$this->installer_config->set('differ_progress_key', -1);
 
 		foreach ($update_files as $type => $files)
 		{
diff --git a/phpBB/phpbb/install/module/update_filesystem/task/download_updated_files.php b/phpBB/phpbb/install/module/update_filesystem/task/download_updated_files.php
index 4d7f0e0cdf..ed61d381dc 100644
--- a/phpBB/phpbb/install/module/update_filesystem/task/download_updated_files.php
+++ b/phpBB/phpbb/install/module/update_filesystem/task/download_updated_files.php
@@ -87,7 +87,8 @@ class download_updated_files extends task_base
 			$file_update_info = $this->installer_config->get('update_files', array());
 
 			// Display download box only if the archive won't be empty
-			if (!empty($file_update_info) && !(isset($file_update_info['delete']) && count($file_update_info) == 1))
+			$display_download_link = !empty($file_update_info) && !(isset($file_update_info['delete']) && count($file_update_info) == 1);
+			if ($display_download_link)
 			{
 				// Render download box
 				$this->iohandler->add_download_link(
@@ -107,7 +108,7 @@ class download_updated_files extends task_base
 				'database_update_submit'	=> array(
 					'label'		=> 'UPDATE_CONTINUE_UPDATE_PROCESS',
 					'type'		=> 'submit',
-					'disabled'	=> !empty($file_update_info),
+					'disabled'	=> $display_download_link,
 				),
 			));
 
diff --git a/phpBB/phpbb/install/module/update_filesystem/task/update_files.php b/phpBB/phpbb/install/module/update_filesystem/task/update_files.php
index fbb465cc66..3acb965f6b 100644
--- a/phpBB/phpbb/install/module/update_filesystem/task/update_files.php
+++ b/phpBB/phpbb/install/module/update_filesystem/task/update_files.php
@@ -172,11 +172,15 @@ class update_files extends task_base
 							$this->file_updater->update_file($path, $new_path . $path);
 						break;
 						case 'update_with_diff':
+							$cache_diff_filename = '_file_' . md5($path);
+							if ($this->cache->_exists($cache_diff_filename))
+							{
 							$this->file_updater->update_file(
 								$path,
-								base64_decode($this->cache->get('_file_' . md5($path))),
+									base64_decode($this->cache->get($cache_diff_filename)),
 								true
 							);
+							}
 						break;
 					}