diff --git a/dockerfiles/fluentd-mozdef/Gemfile.lock b/dockerfiles/fluentd-mozdef/Gemfile.lock
index 81558acda..7a656721e 100644
--- a/dockerfiles/fluentd-mozdef/Gemfile.lock
+++ b/dockerfiles/fluentd-mozdef/Gemfile.lock
@@ -6,8 +6,8 @@ GEM
       i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-    addressable (2.6.0)
-      public_suffix (>= 2.0.2, < 4.0)
+    addressable (2.8.0)
+      public_suffix (>= 2.0.2, < 5.0)
     aws-eventstream (1.0.3)
     aws-sdk (2.11.273)
       aws-sdk-resources (= 2.11.273)
@@ -77,7 +77,7 @@ GEM
     msgpack (1.2.10)
     netrc (0.11.0)
     oj (3.5.1)
-    public_suffix (3.0.3)
+    public_suffix (4.0.6)
     recursive-open-struct (1.0.0)
     rest-client (2.0.2)
       http-cookie (>= 1.0.2, < 2.0)