diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index abded0b..0dd5cd0 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -17,7 +17,7 @@ jobs:
       matrix:
         os: [ ubuntu-16.04, ubuntu-18.04, ubuntu-20.04, macos-10.15, windows-2016, windows-2019 ]
         # Use various version syntax here for testing
-        ruby: [ 2.2, 2.3, 2.4, 2.5, 2.6.6, 2.7, ruby-head, debug, jruby-9.1, jruby, jruby-head, truffleruby, truffleruby-head ]
+        ruby: [ 2.1, 2.2, 2.3, 2.4, 2.5, 2.6.6, 2.7, ruby-head, debug, jruby-9.1, jruby, jruby-head, truffleruby, truffleruby-head ]
         include:
         - { os: ubuntu-18.04, ruby: rubinius }
         - { os: windows-2016, ruby: mingw }
diff --git a/README.md b/README.md
index 43b54d8..a53e210 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ This action currently supports these versions of MRI, JRuby and TruffleRuby:
 
 | Interpreter | Versions |
 | ----------- | -------- |
-| Ruby | 2.2, 2.3.0 - 2.3.8, 2.4.0 - 2.4.10, 2.5.0 - 2.5.8, 2.6.0 - 2.6.6, 2.7.1, head, debug, mingw, mswin |
+| Ruby | 2.1.9, 2.2, 2.3.0 - 2.3.8, 2.4.0 - 2.4.10, 2.5.0 - 2.5.8, 2.6.0 - 2.6.6, 2.7.1, head, debug, mingw, mswin |
 | JRuby | 9.1.17.0, 9.2.9.0 - 9.2.12.0, head |
 | TruffleRuby | 19.3.0 - 20.1.0, head |
 | Rubinius | 4.14 |
diff --git a/dist/index.js b/dist/index.js
index 8d8804a..75f02a1 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -2377,8 +2377,8 @@ async function installBundler(bundlerVersionInput, platform, rubyPrefix, engine,
     throw new Error(`Cannot parse bundler input: ${bundlerVersion}`)
   }
 
-  if (rubyVersion.startsWith('2.2')) {
-    console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby 2.2')
+  if (rubyVersion.match(/^2\.[12]/)) {
+    console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby <= 2.2')
     bundlerVersion = '1'
   } else if (rubyVersion.startsWith('2.3')) {
     console.log('Ruby 2.3 has a bug with Bundler 2 (https://github.com/rubygems/rubygems/issues/3570), using Bundler 1 instead on Ruby 2.3')
@@ -3093,6 +3093,7 @@ __webpack_require__.r(__webpack_exports__);
 function getVersions(platform) {
   const versions = {
     "ruby": [
+      "2.1.9",
       "2.2.10",
       "2.3.0", "2.3.1", "2.3.2", "2.3.3", "2.3.4", "2.3.5", "2.3.6", "2.3.7", "2.3.8",
       "2.4.0", "2.4.1", "2.4.2", "2.4.3", "2.4.4", "2.4.5", "2.4.6", "2.4.7", "2.4.9", "2.4.10",
@@ -5923,6 +5924,7 @@ exports.getState = getState;
 __webpack_require__.r(__webpack_exports__);
 /* harmony export (binding) */ __webpack_require__.d(__webpack_exports__, "versions", function() { return versions; });
 const versions = {
+  "2.1.9": "https://dl.bintray.com/oneclick/rubyinstaller/ruby-2.1.9-x64-mingw32.7z",
   "2.2.6": "https://dl.bintray.com/oneclick/rubyinstaller/ruby-2.2.6-x64-mingw32.7z",
   "2.3.0": "https://dl.bintray.com/oneclick/rubyinstaller/ruby-2.3.0-x64-mingw32.7z",
   "2.3.1": "https://dl.bintray.com/oneclick/rubyinstaller/ruby-2.3.1-x64-mingw32.7z",
@@ -7549,14 +7551,14 @@ const rubyInstallerVersions = __webpack_require__(471).versions
 // Extract to SSD, see https://github.com/ruby/setup-ruby/pull/14
 const drive = (process.env['GITHUB_WORKSPACE'] || 'C')[0]
 
-// needed for 2.2, 2.3, and mswin, cert file used by Git for Windows
+// needed for 2.1, 2.2, 2.3, and mswin, cert file used by Git for Windows
 const certFile = 'C:\\Program Files\\Git\\mingw64\\ssl\\cert.pem'
 
 // standard MSYS2 location, found by 'devkit.rb'
 const msys2 = 'C:\\msys64'
 const msys2PathEntries = [`${msys2}\\mingw64\\bin`, `${msys2}\\usr\\bin`]
 
-// location & path for old RubyInstaller DevKit (MSYS), Ruby 2.2 and 2.3
+// location & path for old RubyInstaller DevKit (MSYS), Ruby 2.1, 2.2 and 2.3
 const msys = `${drive}:\\DevKit64`
 const msysPathEntries = [`${msys}\\mingw\\x86_64-w64-mingw32\\bin`,
   `${msys}\\mingw\\bin`, `${msys}\\bin`]
@@ -7609,7 +7611,7 @@ async function symLinkToEmbeddedMSYS2() {
 async function setupMingw(version) {
   core.exportVariable('MAKE', 'make.exe')
 
-  if (version.startsWith('2.2') || version.startsWith('2.3')) {
+  if (version.match(/^2\.[123]/)) {
     core.exportVariable('SSL_CERT_FILE', certFile)
     await common.measure('Installing MSYS1', async () =>
       installMSYS(version))
@@ -7625,7 +7627,7 @@ async function setupMingw(version) {
   }
 }
 
-// Ruby 2.2 and 2.3
+// Ruby 2.1, 2.2 and 2.3
 async function installMSYS(version) {
   const url = 'https://dl.bintray.com/oneclick/rubyinstaller/DevKit-mingw64-64-4.7.2-20130224-1432-sfx.exe'
   const downloadPath = await tc.downloadTool(url)
diff --git a/generate-windows-versions.rb b/generate-windows-versions.rb
index 7670156..3ea07b5 100644
--- a/generate-windows-versions.rb
+++ b/generate-windows-versions.rb
@@ -2,7 +2,8 @@ require 'net/http'
 require 'yaml'
 require 'json'
 
-min_version = '2.2.6'
+min_requirements = ['~> 2.1.9', '>= 2.2.6'].map { |req| Gem::Requirement.new(req) }
+
 url = 'https://raw.githubusercontent.com/oneclick/rubyinstaller.org-website/master/_data/downloads.yaml'
 entries = YAML.load(Net::HTTP.get(URI(url)), symbolize_names: true)
 
@@ -19,7 +20,7 @@ versions = entries.select { |entry|
 }.sort_by { |version, entry|
   Gem::Version.new(version)
 }.select { |version, entry|
-  Gem::Version.new(version) >= Gem::Version.new(min_version)
+  min_requirements.any? { |req| req.satisfied_by?(Gem::Version.new(version)) }
 }.map { |version, entry|
   [version, entry[:href]]
 }.to_h
diff --git a/index.js b/index.js
index 89f87a8..4167487 100644
--- a/index.js
+++ b/index.js
@@ -191,8 +191,8 @@ async function installBundler(bundlerVersionInput, platform, rubyPrefix, engine,
     throw new Error(`Cannot parse bundler input: ${bundlerVersion}`)
   }
 
-  if (rubyVersion.startsWith('2.2')) {
-    console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby 2.2')
+  if (rubyVersion.match(/^2\.[12]/)) {
+    console.log('Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby <= 2.2')
     bundlerVersion = '1'
   } else if (rubyVersion.startsWith('2.3')) {
     console.log('Ruby 2.3 has a bug with Bundler 2 (https://github.com/rubygems/rubygems/issues/3570), using Bundler 1 instead on Ruby 2.3')
diff --git a/ruby-builder-versions.js b/ruby-builder-versions.js
index 6913a25..040e97b 100644
--- a/ruby-builder-versions.js
+++ b/ruby-builder-versions.js
@@ -1,6 +1,7 @@
 export function getVersions(platform) {
   const versions = {
     "ruby": [
+      "2.1.9",
       "2.2.10",
       "2.3.0", "2.3.1", "2.3.2", "2.3.3", "2.3.4", "2.3.5", "2.3.6", "2.3.7", "2.3.8",
       "2.4.0", "2.4.1", "2.4.2", "2.4.3", "2.4.4", "2.4.5", "2.4.6", "2.4.7", "2.4.9", "2.4.10",
diff --git a/versions-strings-for-builder.rb b/versions-strings-for-builder.rb
index ba69956..320f35d 100644
--- a/versions-strings-for-builder.rb
+++ b/versions-strings-for-builder.rb
@@ -3,6 +3,7 @@ versions = eval hash
 
 by_minor = versions[:ruby].group_by { |v| v[/^\d\.\d/] }
 
+p by_minor['2.1']
 p by_minor['2.2']
 p by_minor['2.3']
 
diff --git a/windows-versions.js b/windows-versions.js
index 5f3d55f..34d021b 100644
--- a/windows-versions.js
+++ b/windows-versions.js
@@ -1,4 +1,5 @@
 export const versions = {
+  "2.1.9": "https://dl.bintray.com/oneclick/rubyinstaller/ruby-2.1.9-x64-mingw32.7z",
   "2.2.6": "https://dl.bintray.com/oneclick/rubyinstaller/ruby-2.2.6-x64-mingw32.7z",
   "2.3.0": "https://dl.bintray.com/oneclick/rubyinstaller/ruby-2.3.0-x64-mingw32.7z",
   "2.3.1": "https://dl.bintray.com/oneclick/rubyinstaller/ruby-2.3.1-x64-mingw32.7z",
diff --git a/windows.js b/windows.js
index 5cca9f9..0e83a7b 100644
--- a/windows.js
+++ b/windows.js
@@ -13,14 +13,14 @@ const rubyInstallerVersions = require('./windows-versions').versions
 // Extract to SSD, see https://github.com/ruby/setup-ruby/pull/14
 const drive = (process.env['GITHUB_WORKSPACE'] || 'C')[0]
 
-// needed for 2.2, 2.3, and mswin, cert file used by Git for Windows
+// needed for 2.1, 2.2, 2.3, and mswin, cert file used by Git for Windows
 const certFile = 'C:\\Program Files\\Git\\mingw64\\ssl\\cert.pem'
 
 // standard MSYS2 location, found by 'devkit.rb'
 const msys2 = 'C:\\msys64'
 const msys2PathEntries = [`${msys2}\\mingw64\\bin`, `${msys2}\\usr\\bin`]
 
-// location & path for old RubyInstaller DevKit (MSYS), Ruby 2.2 and 2.3
+// location & path for old RubyInstaller DevKit (MSYS), Ruby 2.1, 2.2 and 2.3
 const msys = `${drive}:\\DevKit64`
 const msysPathEntries = [`${msys}\\mingw\\x86_64-w64-mingw32\\bin`,
   `${msys}\\mingw\\bin`, `${msys}\\bin`]
@@ -73,7 +73,7 @@ async function symLinkToEmbeddedMSYS2() {
 async function setupMingw(version) {
   core.exportVariable('MAKE', 'make.exe')
 
-  if (version.startsWith('2.2') || version.startsWith('2.3')) {
+  if (version.match(/^2\.[123]/)) {
     core.exportVariable('SSL_CERT_FILE', certFile)
     await common.measure('Installing MSYS1', async () =>
       installMSYS(version))
@@ -89,7 +89,7 @@ async function setupMingw(version) {
   }
 }
 
-// Ruby 2.2 and 2.3
+// Ruby 2.1, 2.2 and 2.3
 async function installMSYS(version) {
   const url = 'https://dl.bintray.com/oneclick/rubyinstaller/DevKit-mingw64-64-4.7.2-20130224-1432-sfx.exe'
   const downloadPath = await tc.downloadTool(url)