diff --git a/Tmain/optscript-scope.d/exit-expected.txt b/Tmain/optscript-scope.d/exit-expected.txt
new file mode 100644
index 0000000000..573541ac97
--- /dev/null
+++ b/Tmain/optscript-scope.d/exit-expected.txt
@@ -0,0 +1 @@
+0
diff --git a/Tmain/optscript-scope.d/input.unknown b/Tmain/optscript-scope.d/input.unknown
new file mode 100644
index 0000000000..1ae77bed3a
--- /dev/null
+++ b/Tmain/optscript-scope.d/input.unknown
@@ -0,0 +1,11 @@
+* TITLE 0
++ Subtitle 0.0
++ Subtitle 0.1
+- subsubtitle 0.1.0
+- subsubtitle 0.1.1
++ Subtitle 0.2
+- subsubtitle 0.2.0
+* TITLE 1
++ Subtitle 1.0
+- subsubtitle 1.0.0
+- subsubtitle 1.0.1
diff --git a/Tmain/optscript-scope.d/run.sh b/Tmain/optscript-scope.d/run.sh
new file mode 100755
index 0000000000..f05f1c83cf
--- /dev/null
+++ b/Tmain/optscript-scope.d/run.sh
@@ -0,0 +1,12 @@
+# Copyright: 2024 Masatake YAMATO
+# License: GPL-2
+
+CTAGS=$1
+
+. ../utils.sh
+
+${CTAGS} --quiet --options=NONE \
+		 --sort=no --fields=+n \
+		 --options=./unknown.ctags \
+		 --language-force=UnknownX \
+		 -o - input.unknown
diff --git a/Tmain/optscript-scope.d/stderr-expected.txt b/Tmain/optscript-scope.d/stderr-expected.txt
new file mode 100644
index 0000000000..e2c071a1eb
--- /dev/null
+++ b/Tmain/optscript-scope.d/stderr-expected.txt
@@ -0,0 +1,56 @@
+section-enter
+0
+scopetop: OK
+scopeNth0: OK
+section-leave
+1
+subsection-enter
+1
+scopeNth1: OK
+subsection-leave
+2
+subsection-enter
+2
+scopetop: OK
+scopeNth0: OK
+scopeNth1: OK
+subsection-leave
+2
+subsubsection-enter
+2
+subsubsection-leave
+3
+subsubsection-enter
+3
+subsubsection-leave
+3
+subsection-enter
+3
+scopetop: OK
+scopeNth0: OK
+scopeNth1: OK
+subsection-leave
+2
+subsubsection-enter
+2
+subsubsection-leave
+3
+section-enter
+3
+scopetop: OK
+scopeNth0: OK
+section-leave
+1
+subsection-enter
+1
+scopeNth1: OK
+subsection-leave
+2
+subsubsection-enter
+2
+subsubsection-leave
+3
+subsubsection-enter
+3
+subsubsection-leave
+3
diff --git a/Tmain/optscript-scope.d/stdout-expected.txt b/Tmain/optscript-scope.d/stdout-expected.txt
new file mode 100644
index 0000000000..3334b3eb17
--- /dev/null
+++ b/Tmain/optscript-scope.d/stdout-expected.txt
@@ -0,0 +1,11 @@
+TITLE 0	input.unknown	/^* TITLE 0$/;"	s	line:1
+Subtitle 0.0	input.unknown	/^+ Subtitle 0.0$/;"	t	line:2	section:TITLE 0
+Subtitle 0.1	input.unknown	/^+ Subtitle 0.1$/;"	t	line:3	section:TITLE 0
+subsubtitle 0.1.0	input.unknown	/^- subsubtitle 0.1.0$/;"	u	line:4	subsection:TITLE 0.Subtitle 0.1
+subsubtitle 0.1.1	input.unknown	/^- subsubtitle 0.1.1$/;"	u	line:5	subsection:TITLE 0.Subtitle 0.1
+Subtitle 0.2	input.unknown	/^+ Subtitle 0.2$/;"	t	line:6	section:TITLE 0
+subsubtitle 0.2.0	input.unknown	/^- subsubtitle 0.2.0$/;"	u	line:7	subsection:TITLE 0.Subtitle 0.2
+TITLE 1	input.unknown	/^* TITLE 1$/;"	s	line:8
+Subtitle 1.0	input.unknown	/^+ Subtitle 1.0$/;"	t	line:9	section:TITLE 1
+subsubtitle 1.0.0	input.unknown	/^- subsubtitle 1.0.0$/;"	u	line:10	subsection:TITLE 1.Subtitle 1.0
+subsubtitle 1.0.1	input.unknown	/^- subsubtitle 1.0.1$/;"	u	line:11	subsection:TITLE 1.Subtitle 1.0
diff --git a/Tmain/optscript-scope.d/unknown.ctags b/Tmain/optscript-scope.d/unknown.ctags
new file mode 100644
index 0000000000..313ecb05ed
--- /dev/null
+++ b/Tmain/optscript-scope.d/unknown.ctags
@@ -0,0 +1,56 @@
+--langdef=UnknownX
+--kinddef-UnknownX=s,section,sections
+--kinddef-UnknownX=t,subsection,subsections
+--kinddef-UnknownX=u,subsubsection,subsubsections
+
+--regex-UnknownX=/^\* (.*)$/\1/s/{{
+   /section-enter = _scopedepth =
+   . _scopeset
+   _scopetop {
+      (scopetop: OK) =
+      . eq {
+         (scopeNth0: OK) =
+      } {
+         (scopeNth0: FAILED) =
+      } ifelse
+   } {
+      (scopetop: FAILED) =
+   } ifelse
+   /section-leave = _scopedepth =
+}}
+
+--regex-UnknownX=/^\+ (.*)$/\1/t/{{
+   /subsection-enter = _scopedepth =
+   _scopedepth 3 eq {
+      _scopepop
+   } if
+   _scopedepth 2 eq {
+      0 _scopeNth _scopetop {
+        (scopetop: OK) =
+        eq {
+           (scopeNth0: OK) =
+        } {
+           (scopeNth0: FAILED) =
+        } ifelse
+      } {
+         (scopetop: FAILED) =
+      } ifelse
+      _scopepop
+   } if
+   . _scopepush
+   1 _scopeNth . :scope eq {
+      (scopeNth1: OK) =
+   } {
+      (scopeNth1: FAILED) =
+   } ifelse
+   /subsection-leave = _scopedepth =
+}}
+
+--regex-UnknownX=/^\- (.*)$/\1/u/{{
+   /subsubsection-enter = _scopedepth =
+   _scopedepth 3 eq {
+      _scopepop
+   } if
+   . _scopepush
+   /subsubsection-leave = _scopedepth =
+}}
diff --git a/main/lregex.c b/main/lregex.c
index 2d6c84f509..8d23ea568a 100644
--- a/main/lregex.c
+++ b/main/lregex.c
@@ -3858,17 +3858,18 @@ static EsObject* lrop_get_scope_depth (OptVM *vm, EsObject *name)
 {
 	struct lregexControlBlock *lcb = get_current_lcb (vm);
 	int scope = lcb->currentScope;
+	int depth = 0;
 
 	while (scope != CORK_NIL)
 	{
 		tagEntryInfo *e = getEntryInCorkQueue (scope);
 		if (!e)
 			break;
-
+		depth++;
 		scope = e->extensionFields.scopeIndex;
 	}
 
-	EsObject *q = es_integer_new (scope);
+	EsObject *q = es_integer_new (depth);
 	if (es_error_p(q))
 		return q;