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)