diff --git a/Gemfile b/Gemfile
index 4b7a7035..b0352037 100644
--- a/Gemfile
+++ b/Gemfile
@@ -32,6 +32,9 @@ gem 'sass-embedded'
 gem 'pstore'
 gem 'logger'
 
+# Not found in Github actions
+gem 'terser'
+
 group :development do
   gem 'adsf'
   # puma instead of thin, see https://github.com/nanoc/nanoc/issues/1499
diff --git a/Gemfile.lock b/Gemfile.lock
index 41c2555a..414d685f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -178,6 +178,8 @@ GEM
     stringio (3.1.1)
     terminal-notifier (2.0.0)
     terminal-notifier-guard (1.7.0)
+    terser (1.2.3)
+      execjs (>= 0.3.0, < 3)
     thor (1.3.2)
     tty-color (0.6.0)
     tty-command (0.10.1)
@@ -229,6 +231,7 @@ DEPENDENCIES
   sassc
   terminal-notifier
   terminal-notifier-guard
+  terser
   typogruby
   tzinfo
   tzinfo-data
diff --git a/gemset.nix b/gemset.nix
index 293c3649..70c32eda 100644
--- a/gemset.nix
+++ b/gemset.nix
@@ -875,6 +875,17 @@
     };
     version = "1.7.0";
   };
+  terser = {
+    dependencies = ["execjs"];
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "176swgmwq0cc4z2134x12j9vjvx5y3nrlpbb8p6p0zhsn2wi2cf0";
+      type = "gem";
+    };
+    version = "1.2.3";
+  };
   thor = {
     groups = ["default" "nanoc"];
     platforms = [];