diff --git a/packages/context/src/__tests__/unit/inject.unit.ts b/packages/context/src/__tests__/unit/inject.unit.ts
index 59d9272fed3e..9fb1ae327451 100644
--- a/packages/context/src/__tests__/unit/inject.unit.ts
+++ b/packages/context/src/__tests__/unit/inject.unit.ts
@@ -29,6 +29,16 @@ describe('function argument injection', () => {
     expect(meta.map(m => m.bindingSelector)).to.deepEqual(['foo']);
   });
 
+  it('allows decorator to be explicitly invoked for class ctor args', () => {
+    class TestClass {
+      constructor(foo: string) {}
+    }
+    inject('foo')(TestClass, undefined, 0);
+
+    const meta = describeInjectedArguments(TestClass);
+    expect(meta.map(m => m.bindingSelector)).to.deepEqual(['foo']);
+  });
+
   it('can retrieve information about injected method arguments', () => {
     class TestClass {
       test(@inject('foo') foo: string) {}
diff --git a/packages/context/src/inject.ts b/packages/context/src/inject.ts
index d6d06a95d3b1..e6c6285196b2 100644
--- a/packages/context/src/inject.ts
+++ b/packages/context/src/inject.ts
@@ -124,7 +124,7 @@ export function inject(
   }
   return function markParameterOrPropertyAsInjected(
     target: Object,
-    member: string,
+    member: string | undefined,
     methodDescriptorOrParameterIndex?:
       | TypedPropertyDescriptor<BoundValue>
       | number,