diff --git a/management/backup.py b/management/backup.py
index f352fb41..bb08c13d 100755
--- a/management/backup.py
+++ b/management/backup.py
@@ -186,7 +186,7 @@ def get_passphrase(env):
 	# length of 32 bytes.
 	backup_root = os.path.join(env["STORAGE_ROOT"], 'backup')
 	with open(os.path.join(backup_root, 'secret_key.txt'), encoding="utf-8") as f:
-		passphrase = f.readline().strip()
+		passphrase = f.readline(5_000_000).strip()
 	if len(passphrase) < 43: raise Exception("secret_key.txt's first line is too short!")
 
 	return passphrase
diff --git a/management/mail_log.py b/management/mail_log.py
index e127af3b..9f8b176c 100755
--- a/management/mail_log.py
+++ b/management/mail_log.py
@@ -587,7 +587,7 @@ def readline(filename):
     """
     with open(filename, errors='replace', encoding='utf-8') as file:
         while True:
-          line = file.readline()
+          line = file.readline(5_000_000)
           if not line:
               break
           yield line