diff --git a/lib/loader.js b/lib/loader.js
index 51c8144..fc56041 100644
--- a/lib/loader.js
+++ b/lib/loader.js
@@ -1,4 +1,5 @@
 const path = require('path');
+const url = require('url');
 
 class Loader {
   constructor(options) {
@@ -11,16 +12,7 @@ class Loader {
 
   load(modulePath) {
     if ((this.alwaysImport && !modulePath.endsWith('.json')) || modulePath.endsWith('.mjs')) {
-      let importSpecifier;
-
-      if (modulePath.indexOf(path.sep) === -1 && modulePath.indexOf('/') === -1) {
-        importSpecifier = modulePath;
-      } else {
-        // The ES module spec requires import paths to be valid URLs. As of v14,
-        // Node enforces this on Windows but not on other OSes. On OS X, import
-        // paths that are URLs must not contain parent directory references.
-        importSpecifier = `file://${this.resolvePath_(modulePath)}`;
-      }
+      const importSpecifier = this.resolveImportSpecifier_(modulePath);
 
       return this.import_(importSpecifier)
         .then(
@@ -47,6 +39,25 @@ class Loader {
       });
     }
   }
+
+  resolveImportSpecifier_(modulePath) {
+    const isNamespaced = modulePath.startsWith('@');
+    const isRelative = modulePath.startsWith('.');
+    const hasExtension = /\.[A-Za-z]+/.test(modulePath);
+
+    const resolvedModulePath = hasExtension || isRelative
+      ? this.resolvePath_(modulePath)
+      : modulePath;
+
+    if (isNamespaced || ! hasExtension) {
+      return resolvedModulePath;
+    }
+
+    // The ES module spec requires import paths to be valid URLs. As of v14,
+    // Node enforces this on Windows but not on other OSes. On OS X, import
+    // paths that are URLs must not contain parent directory references.
+    return url.pathToFileURL(resolvedModulePath).toString();
+  }
 }
 
 function requireShim(modulePath) {
diff --git a/spec/loader_spec.js b/spec/loader_spec.js
index 2164abd..9240860 100644
--- a/spec/loader_spec.js
+++ b/spec/loader_spec.js
@@ -1,4 +1,5 @@
 const path = require('path');
+const url = require('url');
 const Loader = require('../lib/loader');
 
 describe('loader', function() {
@@ -55,6 +56,21 @@ describe('loader', function() {
         expect(importShim).toHaveBeenCalledWith('some-module');
       });
 
+      it('imports namespaced modules', async function() {
+        const payload = {default: {}};
+        const requireShim = jasmine.createSpy('requireShim');
+        const importShim = jasmine.createSpy('importShim')
+          .and.returnValue(Promise.resolve(payload));
+        const loader = new Loader({requireShim, importShim});
+        loader.alwaysImport = true;
+
+        const result = await loader.load('@namespace/some-module');
+
+        expect(result).toBe(payload.default);
+        expect(requireShim).not.toHaveBeenCalled();
+        expect(importShim).toHaveBeenCalledWith('@namespace/some-module');
+      });
+
       it('uses require to load JSON files', async function() {
         const requireShim = jasmine.createSpy('requireShim')
           .and.returnValue(Promise.resolve());
@@ -101,6 +117,19 @@ describe('loader', function() {
           expect(importShim).not.toHaveBeenCalled();
         });
 
+        it('loads namespaced commonjs module', async function () {
+          const requireShim = jasmine.createSpy('requireShim')
+            .and.returnValue(Promise.resolve());
+          const importShim = jasmine.createSpy('importShim');
+          const loader = new Loader({requireShim, importShim});
+          loader.alwaysImport = false;
+
+          await expectAsync(loader.load('@namespace/some-module')).toBeResolved();
+
+          expect(requireShim).toHaveBeenCalledWith('@namespace/some-module');
+          expect(importShim).not.toHaveBeenCalled();
+        });
+
         it('propagates the error when import fails', async function () {
           const underlyingError = new Error('nope');
           const requireShim = jasmine.createSpy('requireShim')
@@ -135,18 +164,18 @@ function esModuleSharedExamples(extension, alwaysImport) {
 
     expect(requireShim).not.toHaveBeenCalled();
     expect(resolvePath).toHaveBeenCalledWith(requestedPath);
-    expect(importShim).toHaveBeenCalledWith('file:///the/path/to/the/module');
+    expect(importShim).toHaveBeenCalledWith(url.pathToFileURL('/the/path/to/the/module').toString());
     await expectAsync(loaderPromise).toBePending();
 
     resolve({});
 
     await expectAsync(loaderPromise).toBeResolved();
   }
-  
+
   it('loads the file as an es module', async function () {
     await testBasicEsModuleLoading(path.sep);
   });
-  
+
   it('supports /-separated paths', async function() {
     await testBasicEsModuleLoading('/');
   });