diff --git a/.circleci/config.yml b/.circleci/config.yml
index 1161e4076..3ecea5c9e 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -3,7 +3,7 @@ version: 2
 aliases:
   - &defaults
     docker:
-      - image: circleci/ruby:2.5.1-stretch-node
+      - image: circleci/ruby:2.6.0-stretch-node
         environment: &ruby_environment
           BUNDLE_APP_CONFIG: ./.bundle/
           DB_HOST: localhost
@@ -98,21 +98,21 @@ jobs:
     <<: *defaults
     <<: *install_steps
 
-  install-ruby2.5:
+  install-ruby2.6:
     <<: *defaults
     <<: *install_ruby_dependencies
 
-  install-ruby2.4:
+  install-ruby2.5:
     <<: *defaults
     docker:
-      - image: circleci/ruby:2.4.4-stretch-node
+      - image: circleci/ruby:2.5.3-stretch-node
         environment: *ruby_environment
     <<: *install_ruby_dependencies
 
-  install-ruby2.3:
+  install-ruby2.4:
     <<: *defaults
     docker:
-      - image: circleci/ruby:2.3.7-stretch-node
+      - image: circleci/ruby:2.4.5-stretch-node
         environment: *ruby_environment
     <<: *install_ruby_dependencies
 
@@ -128,43 +128,43 @@ jobs:
               - ./mastodon/public/assets
               - ./mastodon/public/packs-test/
 
-  test-ruby2.5:
+  test-ruby2.6:
     <<: *defaults
     docker:
-      - image: circleci/ruby:2.5.1-stretch-node
+      - image: circleci/ruby:2.6.0-stretch-node
         environment: *ruby_environment
-      - image: circleci/postgres:10.3-alpine
+      - image: circleci/postgres:10.6-alpine
         environment:
           POSTGRES_USER: root
-      - image: circleci/redis:4.0.9-alpine
+      - image: circleci/redis:5.0.3-alpine3.8
     <<: *test_steps
 
-  test-ruby2.4:
+  test-ruby2.5:
     <<: *defaults
     docker:
-      - image: circleci/ruby:2.4.4-stretch-node
+      - image: circleci/ruby:2.5.3-stretch-node
         environment: *ruby_environment
-      - image: circleci/postgres:10.3-alpine
+      - image: circleci/postgres:10.6-alpine
         environment:
           POSTGRES_USER: root
-      - image: circleci/redis:4.0.9-alpine
+      - image: circleci/redis:4.0.12-alpine
     <<: *test_steps
 
-  test-ruby2.3:
+  test-ruby2.4:
     <<: *defaults
     docker:
-      - image: circleci/ruby:2.3.7-stretch-node
+      - image: circleci/ruby:2.4.5-stretch-node
         environment: *ruby_environment
-      - image: circleci/postgres:10.3-alpine
+      - image: circleci/postgres:10.6-alpine
         environment:
           POSTGRES_USER: root
-      - image: circleci/redis:4.0.9-alpine
+      - image: circleci/redis:4.0.12-alpine
     <<: *test_steps
 
   test-webui:
     <<: *defaults
     docker:
-      - image: circleci/node:8.11.1-stretch
+      - image: circleci/node:8.15.0-stretch
     steps:
       - *attach_workspace
       - run: ./bin/retry yarn test:jest
@@ -183,20 +183,24 @@ workflows:
   build-and-test:
     jobs:
       - install
-      - install-ruby2.5:
+      - install-ruby2.6:
           requires:
             - install
-      - install-ruby2.4:
+            - install-ruby2.5
+      - install-ruby2.5:
           requires:
             - install
-            - install-ruby2.5
-      - install-ruby2.3:
+      - install-ruby2.4:
           requires:
             - install
             - install-ruby2.5
       - build:
           requires:
             - install-ruby2.5
+      - test-ruby2.6:
+          requires:
+            - install-ruby2.6
+            - build
       - test-ruby2.5:
           requires:
             - install-ruby2.5
@@ -205,10 +209,6 @@ workflows:
           requires:
             - install-ruby2.4
             - build
-      - test-ruby2.3:
-          requires:
-            - install-ruby2.3
-            - build
       - test-webui:
           requires:
             - install
diff --git a/Gemfile b/Gemfile
index bd0ff0967..ceef9d551 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 source 'https://rubygems.org'
-ruby '>= 2.3.0', '< 2.6.0'
+ruby '>= 2.4.0', '< 2.7.0'
 
 gem 'pkg-config', '~> 1.3'