diff --git a/packages/core/src/Injector.ts b/packages/core/src/Injector.ts
index 935cbb4..423824a 100644
--- a/packages/core/src/Injector.ts
+++ b/packages/core/src/Injector.ts
@@ -120,6 +120,10 @@ export function provide<
     getOwnPropertyDescriptor(target, prop) {
       if (prop === inject) return { configurable: true };
       return Reflect.getOwnPropertyDescriptor(target, prop);
+    },
+    has(target, prop) {
+      if (prop === inject) return true;
+      return Reflect.has(target, prop);
     }
   }) as InjectableFunction<Func, Tags>;
 }
diff --git a/packages/core/src/JsObject.ts b/packages/core/src/JsObject.ts
index 4ca88a8..919ca2a 100644
--- a/packages/core/src/JsObject.ts
+++ b/packages/core/src/JsObject.ts
@@ -122,7 +122,7 @@ export function has<Prop extends PropertyKey>(
   value: object,
   property: Prop
 ): value is Record<Prop, unknown> {
-  return Object.hasOwn(value, property);
+  return property in value;
 }
 
 /**
diff --git a/packages/core/src/JsPromise.test.ts b/packages/core/src/JsPromise.test.ts
new file mode 100644
index 0000000..1858ae8
--- /dev/null
+++ b/packages/core/src/JsPromise.test.ts
@@ -0,0 +1,11 @@
+import { expect, test } from "bun:test";
+
+import * as JsPromise from "./JsPromise.js";
+
+test("checking if a promise is a promise", () => {
+  expect(JsPromise.isPromise(Promise.resolve("👌"))).toBe(true);
+});
+
+test("checking if a value with a then method is a promise", () => {
+  expect(JsPromise.isPromise({ then() {} })).toBe(true);
+});
diff --git a/packages/core/src/Protocol/ClientAgent.ts b/packages/core/src/Protocol/ClientAgent.ts
index 5c1bd93..96bc4c6 100644
--- a/packages/core/src/Protocol/ClientAgent.ts
+++ b/packages/core/src/Protocol/ClientAgent.ts
@@ -179,6 +179,14 @@ export class ClientAgent extends Fiber.t {
             return Reflect.getOwnPropertyDescriptor(target, property);
         }
       },
+      has(target, property) {
+        switch (property) {
+          case Metadata.symbol:
+            return true;
+          default:
+            return Reflect.has(target, property);
+        }
+      },
       ownKeys(_target) {
         // Prevents enumeration of the proxy. Attempting to enumerate the proxy
         // will throw a `TypeError`, this includes using the rest syntax when
diff --git a/packages/core/src/Protocol/Session.ts b/packages/core/src/Protocol/Session.ts
index 54ddf2b..30b28da 100644
--- a/packages/core/src/Protocol/Session.ts
+++ b/packages/core/src/Protocol/Session.ts
@@ -232,8 +232,8 @@ export class ServerSession<Value> extends Session {
  * type safety.
  */
 type Subprotocol<Value> = Subprotocol.t<
-  JsFunction.Input<ExtractFunctions<Value>>,
-  JsFunction.Output<ExtractFunctions<Value>>
+  JsFunction.Input<OmitDependencies<ExtractFunctions<Value>>>,
+  Awaited<JsFunction.Output<OmitDependencies<ExtractFunctions<Value>>>>
 >;
 
 interface Options<Value> {
@@ -316,6 +316,14 @@ type Local<T> = T extends (...args: infer Args) => infer Return
  */
 type MaybePromise<T> = Awaited<T> | Promise<Awaited<T>>;
 
+/**
+ * Distributes over a union of function types and omits their injected
+ * dependencies.
+ */
+type OmitDependencies<T> = T extends Injector.InjectableFunction
+  ? Injector.InjectedFunction<T>
+  : T;
+
 /**
  * Represents a remote value. A remote value is the inverse of a local value.
  */
diff --git a/packages/core/src/Protocol/Session.typetest.ts b/packages/core/src/Protocol/Session.typetest.ts
index 109c035..e75b81f 100644
--- a/packages/core/src/Protocol/Session.typetest.ts
+++ b/packages/core/src/Protocol/Session.typetest.ts
@@ -1,8 +1,8 @@
-import * as Injector from '../Injector.js';
-import * as Json from '../Json.js';
-import * as Proxy from '../Proxy.js';
-import * as Session from './Session.js';
-import * as Subprotocol from './Subprotocol.js';
+import * as Injector from "../Injector.js";
+import * as Json from "../Json.js";
+import * as Proxy from "../Proxy.js";
+import * as Session from "./Session.js";
+import * as Subprotocol from "./Subprotocol.js";
 
 const protocol = Subprotocol.init({
   connectionMode: Subprotocol.ConnectionMode.ConnectionOriented,
@@ -48,6 +48,12 @@ test("remote function returning object", () => {
   //    ^? const _proxy: RemoteFunction<() => {}>
 });
 
+test("remote function returning a promise", () => {
+  const session = Session.client<() => Promise<{ cat: "🐈" }>>({ protocol });
+  const _proxy = session.createProxy();
+  //    ^? const _proxy: RemoteFunction<() => Promise<{ cat: "🐈"; }>>
+});
+
 test("remote function returning function", async () => {
   const session = Session.client<() => () => null>({ protocol });
   const proxy = session.createProxy();
@@ -272,6 +278,20 @@ test("an injected dependency is removed from the call signature", () => {
   //    ^? const _proxy: RemoteFunction<(a: boolean) => null>
 });
 
+test("an injected dependency is excluded from protocol type checking", () => {
+  type Context = { clientId: string };
+
+  const session = Session.client<
+    Injector.InjectableFunction<
+      (context: Context | undefined, a: boolean) => null,
+      [Injector.Tag<Context>]
+    >
+  >({ protocol });
+
+  const _proxy = session.createProxy();
+  //    ^? const _proxy: RemoteFunction<(a: boolean) => null>
+});
+
 test("returning a proxy from a function", () => {
   class Foo {
     a!: number;
diff --git a/packages/core/src/Proxy.ts b/packages/core/src/Proxy.ts
index 66d0195..29bce6a 100644
--- a/packages/core/src/Proxy.ts
+++ b/packages/core/src/Proxy.ts
@@ -23,6 +23,10 @@ export function proxy<T extends object>(value: T) {
     getOwnPropertyDescriptor(target, prop) {
       if (prop === symbol) return { configurable: true };
       return Reflect.getOwnPropertyDescriptor(target, prop);
+    },
+    has(target, prop) {
+      if (prop === symbol) return true;
+      return Reflect.has(target, prop);
     }
   }) as Proxy<T>;
 }