@@ -200,9 +200,18 @@ export function createFakeJsPlugin({
         )
       } else if ('id' in decl && decl.id) {
         let binding = decl.id
+        if (binding.type === 'TSQualifiedName') {
+          binding = getIdFromTSEntityName(binding)
+        }
+
         binding = sideEffect
           ? t.identifier(`_${getIdentifierIndex('')}`)
-          : (binding as t.Identifier)
+          : binding
+
+        if (binding.type !== 'Identifier') {
+          throw new Error(`Unexpected ${binding.type} declaration id`)
+        }
+
         bindings.push(binding)
       } else {
         const binding = t.identifier('export_default')
 
@@ -381,6 +381,16 @@ declare global {
 }"
 `;
 
+exports[`sub namespace 1`] = `
+"// sub-namespace.d.ts
+//#region tests/fixtures/sub-namespace.d.ts
+declare namespace Foo.Bar {
+  export {};
+}
+//#endregion
+export { Foo };"
+`;
+
 exports[`tree-shaking 1`] = `
 "// index.d.ts
 //#region tests/fixtures/tree-shaking/mod.d.ts
 
@@ -0,0 +1 @@
+export namespace Foo.Bar {}
@@ -528,3 +528,11 @@ test('tsgo with custom path', async () => {
   )
   expect(snapshot).toMatchSnapshot()
 })
+
+test('sub namespace', async () => {
+  const { snapshot } = await rolldownBuild(
+    path.resolve(dirname, 'fixtures/sub-namespace.ts'),
+    [dts({ emitDtsOnly: true })],
+  )
+  expect(snapshot).toMatchSnapshot()
+})