diff --git a/plantuml-mode.el b/plantuml-mode.el
index 67740b0..ff6832b 100644
--- a/plantuml-mode.el
+++ b/plantuml-mode.el
@@ -352,12 +352,16 @@ The opening { or [ has to be the last visible character in the line (whitespace
 might follow).")
     (defvar plantuml-indent-regexp-note-start "^\s*\\(note\s+over\\|note\sas\s.*\\|note\s+\\(\\(?:\\(?:button\\|left\\|right\\|top\\)\\)\\)\\(?:\s+of\\)?\\)"
       "Indentation regex for all plantuml note elements")
-    (defvar plantuml-indent-regexp-group-start "^\s*\\(loop\s+.*\\|group\s+.*\\|par\s*$\\|opt\s+.*\\|alt\s+.*\\|else\\|activate\s+.+\\)"
-      "Indentation regex for plantuml group elements that are defined for sequence diagrams.")
+    (defvar plantuml-indent-regexp-group-start "^\s*\\(alt\\|else\\|opt\\|loop\\|par\\|break\\|critical\\|group\\)\\(?:\s+.+\\|$\\)"
+      "Indentation regex for plantuml group elements that are defined for sequence diagrams.
+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-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-if-start))
     (defvar plantuml-indent-regexp-end "^\s*\\(endif\\|else\\|end\\|end\s+note\\|.*}\\|deactivate\s+.+\\)")
 
diff --git a/test/plantuml-indentation-test.el b/test/plantuml-indentation-test.el
index 53a1cbb..daad927 100644
--- a/test/plantuml-indentation-test.el
+++ b/test/plantuml-indentation-test.el
@@ -387,7 +387,23 @@ package APackage {
 "))
 
 (ert-deftest plantuml-test-block-indentation/alt-end ()
-  "Test correct indentation of an alt-end block."
+  "Test correct indentation of an alt-end block.
+The alt-keyword is NOT followed by some text."
+  (plantuml-test-indent-block
+   "
+alt
+A -> B
+end
+"
+   "
+alt
+  A -> B
+end
+" ))
+
+(ert-deftest plantuml-test-block-indentation/alt-end-with-label ()
+  "Test correct indentation of an alt-end block.
+The alt-keyword is followed by some text."
   (plantuml-test-indent-block
    "
 alt choice 1
@@ -419,7 +435,23 @@ end
 " ))
 
 (ert-deftest plantuml-test-block-indentation/opt ()
-  "Test correct indentation of an opt block."
+  "Test correct indentation of an opt block.
+The opt-keyword is NOT followed by some text."
+  (plantuml-test-indent-block
+   "
+opt
+A -> B
+end
+"
+   "
+opt
+  A -> B
+end
+" ))
+
+(ert-deftest plantuml-test-block-indentation/opt-with-label ()
+  "Test correct indentation of an opt block.
+The opt-keyword is followed by some text."
   (plantuml-test-indent-block
    "
 opt event triggered
@@ -433,7 +465,8 @@ end
 " ))
 
 (ert-deftest plantuml-test-block-indentation/par ()
-  "Test correct indentation of a par block."
+  "Test correct indentation of a par block.
+The par-keyword is NOT followed by some text."
   (plantuml-test-indent-block
    "
 par
@@ -450,6 +483,101 @@ else
 end
 " ))
 
+(ert-deftest plantuml-test-block-indentation/par-with-label ()
+  "Test correct indentation of a par block.
+The par-keyword is followed by some text."
+  (plantuml-test-indent-block
+   "
+par a text label
+A -> B
+else
+C -> B
+end
+"
+   "
+par a text label
+  A -> B
+else
+  C -> B
+end
+" ))
+
+(ert-deftest plantuml-test-block-indentation/group ()
+  "Test correct indentation of a group block.
+The group-keyword is NOT followed by some text."
+  (plantuml-test-indent-block
+   "
+group
+A -> B
+else
+C -> B
+end
+"
+   "
+group
+  A -> B
+else
+  C -> B
+end
+" ))
+
+(ert-deftest plantuml-test-block-indentation/group-with-label ()
+  "Test correct indentation of a group block.
+The group-keyword is followed by some text."
+  (plantuml-test-indent-block
+   "
+group my own label
+A -> B
+else
+C -> B
+end
+"
+   "
+group my own label
+  A -> B
+else
+  C -> B
+end
+" ))
+
+(ert-deftest plantuml-test-block-indentation/critical ()
+  "Test correct indentation of a critical block.
+The critical-keyword is NOT followed by some text."
+  (plantuml-test-indent-block
+   "
+critical
+A -> B
+else
+C -> B
+end
+"
+   "
+critical
+  A -> B
+else
+  C -> B
+end
+" ))
+
+(ert-deftest plantuml-test-block-indentation/critical-with-label ()
+  "Test correct indentation of a critical block.
+The critical-keyword is followed by some text."
+  (plantuml-test-indent-block
+   "
+critical my own label
+A -> B
+else
+C -> B
+end
+"
+   "
+critical my own label
+  A -> B
+else
+  C -> B
+end
+" ))
+
 
 (ert-deftest plantuml-test-block-indentation/alt-else-loop-group ()
   "Test correct indentation of combination of alt-else, loop and group.
diff --git a/test/resources/unindented.plantuml b/test/resources/unindented.plantuml
index 2d1a94d..f449f65 100644
--- a/test/resources/unindented.plantuml
+++ b/test/resources/unindented.plantuml
@@ -1,4 +1,79 @@
 /' This is a manual test for you to test different use-cases '/
+
+participant API
+participant Instance
+
+alt deploy success
+Instance -> API: Deploy successful
+else deploy failure
+Instance -> API: Deploy failed
+else deploy timeout
+Instance -> API: Deploy failed
+end
+
+
+package "kuaishow-common-proto" {
+component Kwai
+component KwaiGo
+component AcFun
+}
+
+package "kwaigo-log-proto" {
+[KwaiGo] ..> [KwaiGo Client->Data] : split
+}
+
+package "kwaigo-api-proto" {
+[KwaiGo] ..> [KwaiGo Client->Server] : split
+}
+
+cloud "log server\n" {
+[KwaiGo Client->Data] -->[KwaiGo Log Server] : upload
+}
+
+cloud "api server\n" {
+[KwaiGo Api Server]
+}
+
+[KwaiGo Client->Server] --> [KwaiGo Api Server] : request
+[KwaiGo Api Server] --> [KwaiGo Client->Server] : response
+
+database "LogSql" {
+folder "Log" {
+[ReportEvent]
+}
+frame "event" {
+[EventPackage]
+}
+
+frame "stat" {
+[StatPackage]
+}
+}
+
+[KwaiGo Log Server] --> [ReportEvent] : save
+[ReportEvent] --> [EventPackage]
+[ReportEvent] --> [StatPackage]
+
+database "ApiSql" {
+folder "kwaigo" {
+[KwaiGoData]
+}
+frame "user" {
+[UserData]
+}
+
+frame "photo" {
+[PhotoData]
+}
+}
+
+[KwaiGo Api Server] --> [KwaiGoData] : request
+[KwaiGoData] --> [KwaiGo Api Server] : compute
+
+[KwaiGoData] --> [UserData]
+[KwaiGoData] --> [PhotoData]
+
+
 Nobody -> [APIGateway]
 
 package APackage {