diff --git a/herb.gemspec b/herb.gemspec
index 2df46d36d..903e7312a 100644
--- a/herb.gemspec
+++ b/herb.gemspec
@@ -31,6 +31,7 @@ Gem::Specification.new do |spec|
     "lib/**/*.rb",
     "lib/**/*.yml",
     "sig/**/*.rbs",
+    "sig/manifest.yaml",
     "src/**/*.{c,h}",
     "ext/**/*.{c,h}",
     "templates/**/*.{rb,erb}",
diff --git a/sig/manifest.yaml b/sig/manifest.yaml
new file mode 100644
index 000000000..cfbdbb7bf
--- /dev/null
+++ b/sig/manifest.yaml
@@ -0,0 +1,13 @@
+dependencies:
+  - name: delegate
+  - name: did_you_mean
+  - name: fileutils
+  - name: json
+  - name: optparse
+  - name: pathname
+  - name: socket
+  - name: stringio
+  - name: tempfile
+  - name: time
+  - name: timeout
+  - name: yaml