diff --git a/Gemfile.lock b/Gemfile.lock
index e505eb2..dff3122 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -157,7 +157,7 @@ GEM
     mini_mime (1.1.5)
     minitest (5.25.1)
     multipart-post (2.4.1)
-    mutex_m (0.2.0)
+    mutex_m (0.3.0)
     net-imap (0.4.18)
       date
       net-protocol