diff --git a/plantuml-mode.el b/plantuml-mode.el
index 4b85dfd..5e34393 100644
--- a/plantuml-mode.el
+++ b/plantuml-mode.el
@@ -363,7 +363,7 @@ or it is followed by line end.")
     (defvar plantuml-indent-regexp-header-start "^\s*\\(?:\\(?:center\\|left\\|right\\)\s+header\\|header\\)$")
     (defvar plantuml-indent-regexp-footer-start "^\s*\\(?:\\(?:center\\|left\\|right\\)\s+footer\\|footer\\)$")
     (defvar plantuml-indent-regexp-legend-start "^\s*\\(?:legend\\|legend\s+\\(?:bottom\\|top\\)\\|legend\s+\\(?:center\\|left\\|right\\)\\|legend\s+\\(?:bottom\\|top\\)\s+\\(?:center\\|left\\|right\\)\\)$")
-    (defvar plantuml-indent-regexp-if-start "^\s*\\(\\(?:.*\\)?\s*\\(?:[<>.*a-z-|]+\\)?\s*\\(?:\\[[a-zA-Z]+\\]\\)?\s+if\s+.*\\)")
+    (defvar plantuml-indent-regexp-oldif-start "^.*if\s+\".*\"\s+then$")
     (defvar plantuml-indent-regexp-start (list plantuml-indent-regexp-block-start
                                                plantuml-indent-regexp-note-start
                                                plantuml-indent-regexp-group-start
@@ -374,7 +374,7 @@ or it is followed by line end.")
                                                plantuml-indent-regexp-header-start
                                                plantuml-indent-regexp-footer-start
                                                plantuml-indent-regexp-legend-start
-                                               plantuml-indent-regexp-if-start))
+                                               plantuml-indent-regexp-oldif-start))
     (defvar plantuml-indent-regexp-end "^\s*\\(?:}\\|endif\\|else\s*.*\\|end\\|end\s+note\\|end\s+box\\|end\s+ref\\|deactivate\s+.+\\|end\s+title\\|endheader\\|endfooter\\|endlegend\\)$")
     (setq plantuml-font-lock-keywords
           `(
diff --git a/test/plantuml-indentation-activity-old-test.el b/test/plantuml-indentation-activity-old-test.el
new file mode 100644
index 0000000..ba38e7f
--- /dev/null
+++ b/test/plantuml-indentation-activity-old-test.el
@@ -0,0 +1,281 @@
+;;; plantuml-indentation-activity-old-test.el --- PlantUML Mode indentation tests   -*- lexical-binding: t; -*-
+
+;; Author: René Schmelzer
+;; Maintainer: Carlo Sciolla (skuro)
+;; URL: https://github.com/skuro/plantuml-mode
+
+;;; Commentary:
+
+;; Test indentation for activity (old version) diagrams.
+
+;;; Code:
+
+
+(ert-deftest plantuml-test-indentation/activity-old-diagram/branches ()
+  "Test correct indentation of plantuml activity-old diagram elements: branches.
+These code examples are taken from www.plantuml.com"
+  (plantuml-test-indent-block
+   "
+if \"Some Test\" then
+-->[true] \"Some Activity\"
+--> \"Another activity\"
+-right-> (*)
+else
+->[false] \"Something else\"
+-->[Ending process] (*)
+endif
+
+(*)  --> \"check input\"
+If \"input is verbose\" then
+--> [Yes] \"turn on verbosity\"
+--> \"run command\"
+else
+--> \"run command\"
+Endif
+-->(*)
+"
+   "
+if \"Some Test\" then
+  -->[true] \"Some Activity\"
+  --> \"Another activity\"
+  -right-> (*)
+else
+  ->[false] \"Something else\"
+  -->[Ending process] (*)
+endif
+
+(*)  --> \"check input\"
+If \"input is verbose\" then
+  --> [Yes] \"turn on verbosity\"
+  --> \"run command\"
+else
+  --> \"run command\"
+Endif
+-->(*)
+"
+   ))
+
+(ert-deftest plantuml-test-indentation/activity-old-diagram/more-on-branches ()
+  "Test correct indentation of plantuml activity-old diagram elements: more on branches.
+These code examples are taken from www.plantuml.com"
+  (plantuml-test-indent-block
+
+   "
+(*) --> if \"Some Test\" then
+
+-->[true] \"activity 1\"
+
+if \"\" then
+-> \"activity 3\" as a3
+else
+if \"Other test\" then
+-left-> \"activity 5\"
+else
+--> \"activity 6\"
+endif
+endif
+
+else
+
+->[false] \"activity 2\"
+
+endif
+
+a3 --> if \"last test\" then
+--> \"activity 7\"
+else
+-> \"activity 8\"
+endif
+"
+   "
+(*) --> if \"Some Test\" then
+
+  -->[true] \"activity 1\"
+
+  if \"\" then
+    -> \"activity 3\" as a3
+  else
+    if \"Other test\" then
+      -left-> \"activity 5\"
+    else
+      --> \"activity 6\"
+    endif
+  endif
+
+else
+
+  ->[false] \"activity 2\"
+
+endif
+
+a3 --> if \"last test\" then
+  --> \"activity 7\"
+else
+  -> \"activity 8\"
+endif
+"
+   ))
+
+(ert-deftest plantuml-test-indentation/activity-old-diagram/partitions ()
+  "Test correct indentation of plantuml activity-old diagram elements: partitions.
+These code examples are taken from www.plantuml.com"
+  (plantuml-test-indent-block
+
+   "
+partition Conductor {
+(*) --> \"Climbs on Platform\"
+--> === S1 ===
+--> Bows
+}
+
+partition Audience #LightSkyBlue {
+=== S1 === --> Applauds
+}
+
+partition Conductor {
+Bows --> === S2 ===
+--> WavesArmes
+Applauds --> === S2 ===
+}
+
+partition Orchestra #CCCCEE {
+WavesArmes --> Introduction
+--> \"Play music\"
+}
+"
+"
+partition Conductor {
+  (*) --> \"Climbs on Platform\"
+  --> === S1 ===
+  --> Bows
+}
+
+partition Audience #LightSkyBlue {
+  === S1 === --> Applauds
+}
+
+partition Conductor {
+  Bows --> === S2 ===
+  --> WavesArmes
+  Applauds --> === S2 ===
+}
+
+partition Orchestra #CCCCEE {
+  WavesArmes --> Introduction
+  --> \"Play music\"
+}
+"))
+
+(ert-deftest plantuml-test-indentation/activity-old-diagram/complete-example ()
+  "Test correct indentation of plantuml activity-old diagram elements: complete example.
+These code examples are taken from www.plantuml.com"
+  (plantuml-test-indent-block
+
+   "
+title Servlet Container
+
+(*) --> \"ClickServlet.handleRequest()\"
+--> \"new Page\"
+
+if \"Page.onSecurityCheck\" then
+->[true] \"Page.onInit()\"
+
+if \"isForward?\" then
+->[no] \"Process controls\"
+
+if \"continue processing?\" then
+-->[yes] ===RENDERING===
+else
+-->[no] ===REDIRECT_CHECK===
+endif
+
+else
+-->[yes] ===RENDERING===
+endif
+
+if \"is Post?\" then
+-->[yes] \"Page.onPost()\"
+--> \"Page.onRender()\" as render
+--> ===REDIRECT_CHECK===
+else
+-->[no] \"Page.onGet()\"
+--> render
+endif
+
+else
+-->[false] ===REDIRECT_CHECK===
+endif
+
+if \"Do redirect?\" then
+->[yes] \"redirect request\"
+--> ==BEFORE_DESTROY===
+else
+if \"Do Forward?\" then
+-left->[yes] \"Forward request\"
+--> ==BEFORE_DESTROY===
+else
+-right->[no] \"Render page template\"
+--> ==BEFORE_DESTROY===
+endif
+endif
+
+--> \"Page.onDestroy()\"
+-->(*)
+"
+   "
+title Servlet Container
+
+(*) --> \"ClickServlet.handleRequest()\"
+--> \"new Page\"
+
+if \"Page.onSecurityCheck\" then
+  ->[true] \"Page.onInit()\"
+
+  if \"isForward?\" then
+    ->[no] \"Process controls\"
+
+    if \"continue processing?\" then
+      -->[yes] ===RENDERING===
+    else
+      -->[no] ===REDIRECT_CHECK===
+    endif
+
+  else
+    -->[yes] ===RENDERING===
+  endif
+
+  if \"is Post?\" then
+    -->[yes] \"Page.onPost()\"
+    --> \"Page.onRender()\" as render
+    --> ===REDIRECT_CHECK===
+  else
+    -->[no] \"Page.onGet()\"
+    --> render
+  endif
+
+else
+  -->[false] ===REDIRECT_CHECK===
+endif
+
+if \"Do redirect?\" then
+  ->[yes] \"redirect request\"
+  --> ==BEFORE_DESTROY===
+else
+  if \"Do Forward?\" then
+    -left->[yes] \"Forward request\"
+    --> ==BEFORE_DESTROY===
+  else
+    -right->[no] \"Render page template\"
+    --> ==BEFORE_DESTROY===
+  endif
+endif
+
+--> \"Page.onDestroy()\"
+-->(*)
+"
+   ))
+
+
+(provide 'plantuml-indentation-activity-old-test)
+
+;;; plantuml-indentation-activity-old-test.el ends here