diff --git a/CITATION.cff b/CITATION.cff
index 3d24c7b..0f817e8 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -3,7 +3,7 @@ message: "If you use this software, please cite it as below."
 
 title: "de:code"
 abstract: "DESHIMA code for data analysis"
-version: 2.9.0
+version: 2.9.1
 date-released: 2023-11-25
 license: "MIT"
 doi: "10.5281/zenodo.3384216"
diff --git a/README.md b/README.md
index fc2b423..6b561b2 100644
--- a/README.md
+++ b/README.md
@@ -11,5 +11,5 @@ DESHIMA code for data analysis
 ## Installation
 
 ```shell
-pip install decode==2.9.0
+pip install decode==2.9.1
 ```
diff --git a/decode/__init__.py b/decode/__init__.py
index 3277d48..e4f640e 100644
--- a/decode/__init__.py
+++ b/decode/__init__.py
@@ -10,7 +10,7 @@
     "select",
     "utils",
 ]
-__version__ = "2.9.0"
+__version__ = "2.9.1"
 
 
 # submodules
diff --git a/pyproject.toml b/pyproject.toml
index edde958..360c19a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "decode"
-version = "2.9.0"
+version = "2.9.1"
 description = "DESHIMA code for data analysis"
 authors = ["Akio Taniguchi <taniguchi@a.phys.nagoya-u.ac.jp>"]
 keywords = [