diff --git a/phpBB/includes/functions_template.php b/phpBB/includes/functions_template.php
index 74f5311dff..31cee929b2 100644
--- a/phpBB/includes/functions_template.php
+++ b/phpBB/includes/functions_template.php
@@ -738,6 +738,8 @@ class template_compile
 		}
 
 		stream_filter_append($source_handle, 'template');
+
+		@flock($destination_handle);
 		stream_copy_to_stream($source_handle, $destination_handle);
 
 		@fclose($source_handle);
@@ -773,4 +775,4 @@ class template_compile
 	}
 }
 
-?>
\ No newline at end of file
+?>