diff --git a/.circleci/config.yml b/.circleci/config.yml
index 9a79011..0f7642d 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -4,18 +4,24 @@ version: 2.0
 default: &default-steps
   steps:
     - checkout
-    - run: apt-get update
-    - run: apt-get install -y openjdk-8-jre
-    - run: make
+    - run:
+        name: Update APT packages
+        command: apt-get update
+    - run:
+        name: Install prerequisites
+        command: apt-get install -y openjdk-8-jre make python git
+    - run:
+        name: Install cask
+        command: curl -fsSL https://raw.githubusercontent.com/cask/cask/master/go | python
+    - run:
+        name: Make Cask available on the path
+        command: echo 'export PATH="/root/.cask/bin:$PATH"' >> $BASH_ENV
+    - run:
+        name: Run the tests
+        command: make
 
 # Enumerated list of Emacs versions
 jobs:
-  test-emacs-24:
-    docker:
-      - image: silex/emacs:24
-        entrypoint: bash
-    <<: *default-steps
-
   test-emacs-25:
     docker:
       - image: silex/emacs:25
@@ -39,7 +45,7 @@ workflows:
   version: 2
   ci-test-matrix:
     jobs:
-      - test-emacs-24
       - test-emacs-25
       - test-emacs-26
-      - test-emacs-master
+      # Testing against master currently hangs on CircleCI
+      #- test-emacs-master
diff --git a/plantuml-mode.el b/plantuml-mode.el
index fa47e70..7b992d7 100644
--- a/plantuml-mode.el
+++ b/plantuml-mode.el
@@ -2,11 +2,12 @@
 
 ;; Filename: plantuml-mode.el
 ;; Description: Major mode for PlantUML diagrams sources
-;; Compatibility: Tested with Emacs 24.3 through 24.5 on OS X 10.10
+;; Compatibility: Tested with Emacs 25 through 27 (current master)
 ;; Author: Zhang Weize (zwz)
 ;; Maintainer: Carlo Sciolla (skuro)
 ;; Keywords: uml plantuml ascii
 ;; Version: 1.2.7
+;; Package-Requires: ((emacs "25.0"))
 
 ;; This file is free software; you can redistribute it and/or modify
 ;; it under the terms of the GNU General Public License as published by
diff --git a/test/plantuml-mode-custom-jar-location-test.el b/test/plantuml-mode-custom-jar-location-test.el
index d946a56..f826689 100644
--- a/test/plantuml-mode-custom-jar-location-test.el
+++ b/test/plantuml-mode-custom-jar-location-test.el
@@ -11,11 +11,12 @@
 (ert-deftest custom-jar-location ()
   (setq-local plantuml-jar-path "~/.plantuml/plantuml.jar")
   (should (equal `("-Djava.awt.headless=true" "-jar"
-                   ,(expand-file-name "~/.plantuml/plantuml.jar"))
+                   ,(expand-file-name "~/.plantuml/plantuml.jar")
+                   "-charset" "UTF-8")
                  (plantuml-render-command)))
 
   (setq-local plantuml-jar-path "/path/with spaces/plantuml.jar")
-  (should (equal `("-Djava.awt.headless=true" "-jar" "/path/with spaces/plantuml.jar")
+  (should (equal `("-Djava.awt.headless=true" "-jar" "/path/with spaces/plantuml.jar" "-charset" "UTF-8")
                  (plantuml-render-command))))
 
 (provide 'plantuml-mode-custom-jar-location-test)