diff --git a/plantuml-mode.el b/plantuml-mode.el
index 6e25a89..09281f7 100644
--- a/plantuml-mode.el
+++ b/plantuml-mode.el
@@ -222,7 +222,7 @@ default output type for new buffers."
                   plantuml-java-command
                   ,@plantuml-java-args
                   (expand-file-name plantuml-jar-path)
-                  (plantuml-output-type-opt) "-p"))
+                  (plantuml-output-type-opt) "-charset" "UTF-8" "-p"))
 
 (defun plantuml-preview-string (prefix string)
   "Preview diagram from PlantUML sources (as STRING), using prefix (as PREFIX)
diff --git a/test/resources/unicode.txt b/test/resources/unicode.txt
new file mode 100644
index 0000000..f6c945e
--- /dev/null
+++ b/test/resources/unicode.txt
@@ -0,0 +1,9 @@
+     ┌────┐          ┌───┐
+     │lang│          │日本語│
+     └─┬──┘          └─┬─┘
+       │               │
+       │ ─────────────>│
+     ┌─┴──┐          ┌─┴─┐
+     │lang│          │日本語│
+     └────┘          └───┘
+