diff --git a/lib/importmap/engine.rb b/lib/importmap/engine.rb
index 2828868..46ceb2b 100755
--- a/lib/importmap/engine.rb
+++ b/lib/importmap/engine.rb
@@ -10,6 +10,7 @@ class Engine < ::Rails::Engine
     config.importmap.sweep_cache = Rails.env.development? || Rails.env.test?
     config.importmap.cache_sweepers = []
     config.importmap.rescuable_asset_errors = []
+    config.importmap.accept = %w( js )
 
     config.autoload_once_paths = %W( #{root}/app/helpers )
 
diff --git a/lib/importmap/map.rb b/lib/importmap/map.rb
index 60b7dbd..e7e94ef 100644
--- a/lib/importmap/map.rb
+++ b/lib/importmap/map.rb
@@ -26,7 +26,7 @@ def draw(path = nil, &block)
 
   def pin(name, to: nil, preload: false)
     clear_cache
-    @packages[name] = MappedFile.new(name: name, path: to || "#{name}.js", preload: preload)
+    @packages[name] = MappedFile.new(name: name, path: to || javascript_filename(name), preload: preload)
   end
 
   def pin_all_from(dir, under: nil, to: nil, preload: false)
@@ -73,10 +73,8 @@ def digest(resolver:)
   # and test to ensure the map caches are reset when javascript files are changed.
   def cache_sweeper(watches: nil)
     if watches
-      @cache_sweeper =
-        Rails.application.config.file_watcher.new([], Array(watches).collect { |dir| [ dir.to_s, "js"] }.to_h) do
-          clear_cache
-        end
+      watches = Array(watches).collect { |dir| [ dir.to_s, accepted_extensions] }.to_h
+      @cache_sweeper = Rails.application.config.file_watcher.new([], watches) { clear_cache }
     else
       @cache_sweeper
     end
@@ -137,7 +135,7 @@ def expanded_packages_and_directories
     def expand_directories_into(paths)
       @directories.values.each do |mapping|
         if (absolute_path = absolute_root_of(mapping.dir)).exist?
-          find_javascript_files_in_tree(absolute_path).each do |filename|
+          find_accepted_files_in_tree(absolute_path).each do |filename|
             module_filename = filename.relative_path_from(absolute_path)
             module_name     = module_name_from(module_filename, mapping)
             module_path     = module_path_from(module_filename, mapping)
@@ -149,18 +147,30 @@ def expand_directories_into(paths)
     end
 
     def module_name_from(filename, mapping)
-      [ mapping.under, filename.to_s.remove(filename.extname).remove(/\/?index$/).presence ].compact.join("/")
+      [ mapping.under, filename.to_s.remove(accepted_extensions_pattern).remove(/\/?index$/).presence ].compact.join("/")
     end
 
     def module_path_from(filename, mapping)
-      [ mapping.path || mapping.under, filename.to_s ].compact.join("/")
+      [ mapping.path || mapping.under, javascript_filename(filename.to_s) ].compact.join("/")
     end
 
-    def find_javascript_files_in_tree(path)
-      Dir[path.join("**/*.js{,m}")].collect { |file| Pathname.new(file) }.select(&:file?)
+    def find_accepted_files_in_tree(path)
+      Dir[path.join("**/*.{#{accepted_extensions.join(',')}}")].map(&Pathname.method(:new)).select(&:file?)
     end
 
     def absolute_root_of(path)
       (pathname = Pathname.new(path)).absolute? ? pathname : Rails.root.join(path)
     end
+
+    def accepted_extensions
+      Rails.application.config.importmap.accept
+    end
+
+    def accepted_extensions_pattern
+      /\.(#{accepted_extensions.map(&Regexp.method(:escape)).join('|')})\z/
+    end
+
+    def javascript_filename(name)
+      "#{name.remove(accepted_extensions_pattern)}.js"
+    end
 end
diff --git a/test/cache_sweeper_test.rb b/test/cache_sweeper_test.rb
new file mode 100644
index 0000000..0ef8b7b
--- /dev/null
+++ b/test/cache_sweeper_test.rb
@@ -0,0 +1,43 @@
+require "test_helper"
+
+class CacheSweeperTest < ActiveSupport::TestCase
+
+  test "sweep is triggered when asset with extra extension changes" do
+    previous_accept = Rails.application.config.importmap.accept
+    Rails.application.config.importmap.accept += %w[jsx]
+
+    @importmap = Importmap::Map.new.tap do |map|
+      map.draw do
+        pin "application"
+        pin "components/Clock"
+      end
+    end
+
+    @importmap.cache_sweeper watches: %w[app/javascript vendor/javascript].map(&Rails.root.method(:join))
+
+    resolver = MockResolver.new(%r{components/Clock\.js\z})
+    imports = generate_imports(resolver: resolver)
+    touch_asset 'components/Clock.jsx'
+    new_imports = generate_imports(resolver: resolver)
+
+    assert_not_nil imports["components/Clock"]
+    assert_not_nil new_imports["components/Clock"]
+    assert_not_nil imports["application"]
+    assert_not_nil new_imports["application"]
+    assert_not_equal imports["components/Clock"], new_imports["components/Clock"]
+    assert_equal imports["application"], new_imports["application"]
+  ensure
+    Rails.application.config.importmap.accept = previous_accept
+  end
+
+  private
+    def touch_asset(name)
+      FileUtils.touch Rails.root.join('app', 'javascript', name)
+      sleep 3
+      @importmap.cache_sweeper.execute_if_updated
+    end
+
+    def generate_imports(resolver: ApplicationController.helpers)
+      JSON.parse(@importmap.to_json(resolver: resolver))["imports"]
+    end
+end
diff --git a/test/dummy/app/javascript/components/Clock.jsx b/test/dummy/app/javascript/components/Clock.jsx
new file mode 100644
index 0000000..fc072f8
--- /dev/null
+++ b/test/dummy/app/javascript/components/Clock.jsx
@@ -0,0 +1,12 @@
+import { Component } from "react";
+
+export default class Clock extends Component {
+  render() {
+    return (
+      <div>
+        <h1>UNIX Clock</h1>
+        <p>The current UNIX date is {Date.now()}.</p>
+      </div>
+    );
+  }
+}
diff --git a/test/dummy/app/javascript/components/index.jsx b/test/dummy/app/javascript/components/index.jsx
new file mode 100644
index 0000000..ee65bec
--- /dev/null
+++ b/test/dummy/app/javascript/components/index.jsx
@@ -0,0 +1,7 @@
+import { render } from "react-dom";
+import Clock from "components/Clock";
+
+render(
+  <Clock />,
+  document.getElementById('root')
+);
diff --git a/test/importmap_test.rb b/test/importmap_test.rb
index 1bb1c94..eaf432d 100644
--- a/test/importmap_test.rb
+++ b/test/importmap_test.rb
@@ -13,6 +13,7 @@ def setup
         pin_all_from "app/javascript/spina/controllers", under: "controllers/spina", preload: true
         pin_all_from "app/javascript/spina/controllers", under: "controllers/spina", to: "spina/controllers", preload: true
         pin_all_from "app/javascript/helpers", under: "helpers", preload: true
+        pin_all_from "app/javascript/components", under: "components"
         pin_all_from "lib/assets/javascripts", preload: true
       end
     end
@@ -71,6 +72,27 @@ def setup
     assert_no_match /application/, preloading_module_paths
   end
 
+  test "jsx files are mapped to js when importmap accepts jsx" do
+    previous_accept = Rails.application.config.importmap.accept
+    Rails.application.config.importmap.accept += %w[jsx]
+    @importmap = Importmap::Map.new.tap do |map|
+      map.draw do
+        pin "application"
+        pin_all_from "app/javascript/controllers", under: "controllers", preload: true
+        pin_all_from "app/javascript/components", under: "components"
+      end
+    end
+    importmap_json = generate_importmap_json(resolver: MockResolver.new(%r{components/(Clock|index)\.js\z}))
+    assert_match %r|assets/components/index-.*\.js|, importmap_json["imports"]["components"]
+    assert_match %r|assets/components/Clock-.*\.js|, importmap_json["imports"]["components/Clock"]
+  ensure
+    Rails.application.config.importmap.accept = previous_accept
+  end
+
+  test "jsx files are not mapped when importmap doesn't accept jsx" do
+    assert_nil generate_importmap_json["imports"]["components/Clock"]
+  end
+
   test "digest" do
     assert_match /^\w{40}$/, @importmap.digest(resolver: ApplicationController.helpers)
   end
@@ -98,7 +120,8 @@ def setup
   end
 
   private
-    def generate_importmap_json
-      JSON.parse @importmap.to_json(resolver: ApplicationController.helpers)
+
+    def generate_importmap_json(resolver: ApplicationController.helpers)
+      JSON.parse @importmap.to_json(resolver: resolver)
     end
 end
diff --git a/test/reloader_test.rb b/test/reloader_test.rb
index e2d4dcd..6575cce 100644
--- a/test/reloader_test.rb
+++ b/test/reloader_test.rb
@@ -25,6 +25,6 @@ class ReloaderTest < ActiveSupport::TestCase
   private
     def touch_config
       FileUtils.touch(@config)
-      sleep 1
+      sleep 2
     end
 end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 5519045..cd6b3f7 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -14,3 +14,22 @@
   ActiveSupport::TestCase.file_fixture_path = ActiveSupport::TestCase.fixture_path + "/files"
   ActiveSupport::TestCase.fixtures :all
 end
+
+MockResolver = Struct.new(:pattern) do
+  def path_to_asset(path)
+    if path =~ pattern
+      digest = Digest::SHA256.hexdigest(source_file(path).mtime.to_s)
+      "/assets/" + path.sub(/\.js\z/, "-#{digest}.js")
+    else
+      ApplicationController.helpers.asset_path(path)
+    end
+  end
+
+  def root
+    Rails.root.join('app', 'javascript')
+  end
+
+  def source_file(path)
+    root.join("#{path}x")
+  end
+end