diff --git a/ChangeLog b/ChangeLog
index 1b6e743..ba9ace0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Release 2.2.1 - 2025/03/24
+
+	* in_prometheus_tail_monitor: Add throttling metrics as `fluentd_tail_file_throttled`. (GitHub#227)
+
 Release 2.2.0 - 2024/08/02
 
 	* in_prometheus: Add gzip support (Add a new parameter `content_encoding gzip`)
diff --git a/fluent-plugin-prometheus.gemspec b/fluent-plugin-prometheus.gemspec
index 616ea25..b2e9b86 100644
--- a/fluent-plugin-prometheus.gemspec
+++ b/fluent-plugin-prometheus.gemspec
@@ -1,6 +1,6 @@
 Gem::Specification.new do |spec|
   spec.name          = "fluent-plugin-prometheus"
-  spec.version       = "2.2.0"
+  spec.version       = "2.2.1"
   spec.authors       = ["Masahiro Sano"]
   spec.email         = ["sabottenda@gmail.com"]
   spec.summary       = %q{A fluent plugin that collects metrics and exposes for Prometheus.}