diff --git a/software/debug.php b/software/debug.php
index 32f9fb7..4556bc3 100644
--- a/software/debug.php
+++ b/software/debug.php
@@ -35,7 +35,8 @@ class DumpHTTPRequestToFile {
 
         file_put_contents(
             $targetFile,
-            $data . file_get_contents('php://input') . "\n"
+	    $data . file_get_contents('php://input') . "\n",
+	    FILE_APPEND | LOCK_EX
 	);
 
         //echo("Done!\n\n");