diff --git a/lib/importmap/map.rb b/lib/importmap/map.rb
index 43f0421..6bfa2b1 100644
--- a/lib/importmap/map.rb
+++ b/lib/importmap/map.rb
@@ -30,9 +30,9 @@ def pin(name, to: nil, preload: true)
     @packages[name] = MappedFile.new(name: name, path: to || "#{name}.js", preload: preload)
   end
 
-  def pin_all_from(dir, under: nil, to: nil, preload: true)
+  def pin_all_from(dir, under: nil, to: nil, preserve_extname: false, preload: true)
     clear_cache
-    @directories[dir] = MappedDir.new(dir: dir, under: under, path: to, preload: preload)
+    @directories[dir] = MappedDir.new(dir: dir, under: under, path: to, preserve_extname: preserve_extname, preload: preload)
   end
 
   # Returns an array of all the resolved module paths of the pinned packages. The `resolver` must respond to
@@ -84,7 +84,7 @@ def cache_sweeper(watches: nil)
   end
 
   private
-    MappedDir  = Struct.new(:dir, :path, :under, :preload, keyword_init: true)
+    MappedDir  = Struct.new(:dir, :path, :under, :preserve_extname, :preload, keyword_init: true)
     MappedFile = Struct.new(:name, :path, :preload, keyword_init: true)
 
     def cache_as(name)
@@ -151,7 +151,9 @@ def module_name_from(filename, mapping)
       # folder/index
       index_regex = /(?:\/|^)index$/
 
-      [ mapping.under, filename.to_s.remove(filename.extname).remove(index_regex).presence ].compact.join("/")
+      [ mapping.under, filename.to_s.remove(filename.extname).remove(index_regex).presence ].compact.join("/").tap do |module_name|
+        module_name << filename.extname if mapping.preserve_extname
+      end
     end
 
     def module_path_from(filename, mapping)
diff --git a/test/dummy/vendor/javascript/shoelace/chunks/chunk.2L6GHXIJ.js b/test/dummy/vendor/javascript/shoelace/chunks/chunk.2L6GHXIJ.js
new file mode 100644
index 0000000..e69de29
diff --git a/test/dummy/vendor/javascript/shoelace/components/alert/alert.component.js b/test/dummy/vendor/javascript/shoelace/components/alert/alert.component.js
new file mode 100644
index 0000000..e69de29
diff --git a/test/dummy/vendor/javascript/shoelace/components/alert/alert.js b/test/dummy/vendor/javascript/shoelace/components/alert/alert.js
new file mode 100644
index 0000000..e69de29
diff --git a/test/dummy/vendor/javascript/shoelace/shoelace-autoloader.js b/test/dummy/vendor/javascript/shoelace/shoelace-autoloader.js
new file mode 100644
index 0000000..e69de29
diff --git a/test/importmap_test.rb b/test/importmap_test.rb
index 15c2290..e17aeed 100644
--- a/test/importmap_test.rb
+++ b/test/importmap_test.rb
@@ -15,6 +15,7 @@ def setup
         pin_all_from "app/javascript/helpers", under: "helpers", preload: true
         pin_all_from "lib/assets/javascripts", preload: true
         pin_all_from "app/components", under: "controllers", to: "", preload: true
+        pin_all_from "vendor/javascript/shoelace", under: "shoelace", preserve_extname: true, preload: true
       end
     end
   end
@@ -70,6 +71,14 @@ def setup
     assert_match %r|assets/my_lib-.*\.js|, generate_importmap_json["imports"]["my_lib"]
   end
 
+  test "directory pin respects preserve_extname option" do
+    assert_nil generate_importmap_json["imports"]["shoelace/shoelace-autoloader"]
+    assert_match %r|shoelace/shoelace-autoloader-.*\.js|, generate_importmap_json["imports"]["shoelace/shoelace-autoloader.js"]
+    assert_match %r|shoelace/chunks/chunk.2L6GHXIJ-.*\.js|, generate_importmap_json["imports"]["shoelace/chunks/chunk.2L6GHXIJ.js"]
+    assert_match %r|shoelace/components/alert/alert-.*\.js|, generate_importmap_json["imports"]["shoelace/components/alert/alert.js"]
+    assert_match %r|shoelace/components/alert/alert.component-.*\.js|, generate_importmap_json["imports"]["shoelace/components/alert/alert.component.js"]
+  end
+
   test 'invalid importmap file results in error' do
     file = file_fixture('invalid_import_map.rb')
     importmap = Importmap::Map.new