diff --git a/Gemfile.lock b/Gemfile.lock
index 85cbf25..cf21998 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -136,7 +136,8 @@ GEM
     mini_mime (1.1.5)
     minitest (5.25.5)
     msgpack (1.8.0)
-    mysql2 (0.5.6)
+    mysql2 (0.5.7)
+      bigdecimal
     net-imap (0.5.9)
       date
       net-protocol