diff --git a/docker/exercises/sample_app/Gemfile.lock b/docker/exercises/sample_app/Gemfile.lock
index 02facfa..61ce9a3 100644
--- a/docker/exercises/sample_app/Gemfile.lock
+++ b/docker/exercises/sample_app/Gemfile.lock
@@ -42,8 +42,8 @@ GEM
       i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-    addressable (2.5.2)
-      public_suffix (>= 2.0.2, < 4.0)
+    addressable (2.8.1)
+      public_suffix (>= 2.0.2, < 6.0)
     archive-zip (0.11.0)
       io-like (~> 0.3.0)
     arel (9.0.0)
@@ -107,7 +107,9 @@ GEM
       mimemagic (~> 0.3.2)
     memcachier (0.0.2)
     method_source (0.9.0)
-    mimemagic (0.3.2)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_mime (1.0.1)
     mini_portile2 (2.3.0)
     minitest (5.11.3)
@@ -122,7 +124,7 @@ GEM
       method_source (~> 0.9.0)
     pry-rails (0.3.6)
       pry (>= 0.10.4)
-    public_suffix (3.0.3)
+    public_suffix (4.0.7)
     puma (3.12.0)
     rack (2.0.5)
     rack-protection (2.0.3)