diff --git a/plantuml-mode.el b/plantuml-mode.el
index ff6832b..1edf88c 100644
--- a/plantuml-mode.el
+++ b/plantuml-mode.el
@@ -357,13 +357,15 @@ might follow).")
 Two variants for groups: keyword is either followed by whitespace and some text
 or it is followed by line end.")
     (defvar plantuml-indent-regexp-activate-start "^\s*activate\s+.+$")
+    (defvar plantuml-indent-regexp-box-start "^\s*box\s+.+$")
     (defvar plantuml-indent-regexp-if-start "^\s*\\(\\(?:.*\\)?\s*\\(?:[<>.*a-z-|]+\\)?\s*\\(?:\\[[a-zA-Z]+\\]\\)?\s+if\s+.*\\)")
     (defvar plantuml-indent-regexp-start (list plantuml-indent-regexp-block-start
                                                plantuml-indent-regexp-note-start
                                                plantuml-indent-regexp-group-start
                                                plantuml-indent-regexp-activate-start
+                                               plantuml-indent-regexp-box-start
                                                plantuml-indent-regexp-if-start))
-    (defvar plantuml-indent-regexp-end "^\s*\\(endif\\|else\\|end\\|end\s+note\\|.*}\\|deactivate\s+.+\\)")
+    (defvar plantuml-indent-regexp-end "^\s*\\(endif\\|else\\|end\\|end\s+note\\|end\s+box\\|.*}\\|deactivate\s+.+\\)")
 
     (setq plantuml-font-lock-keywords
           `(
diff --git a/test/plantuml-indentation-test.el b/test/plantuml-indentation-test.el
index daad927..3f54837 100644
--- a/test/plantuml-indentation-test.el
+++ b/test/plantuml-indentation-test.el
@@ -331,6 +331,22 @@ abstract class Foo {
 }
 "))
 
+(ert-deftest platuml-test-block-indentation/box ()
+  "Test correct indentation of a box block"
+  (plantuml-test-indent-block
+   "
+box \"Device with USB connector\"
+actor Human
+participant UsbDetector
+end box
+"
+   "
+box \"Device with USB connector\"
+  actor Human
+  participant UsbDetector
+end box
+" ))
+
 (ert-deftest plantuml-test-block-indentation/various-keywords ()
   "Test correct indentation of block keywords."
   (plantuml-test-indent-block