diff --git a/package.json b/package.json
index fec20ca..74d5c4c 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@ticketbridge/hyper-durable",
-  "version": "0.1.10",
+  "version": "0.1.11",
   "description": "Object-like access to Durable Object properties and methods",
   "repository": {
     "type": "git",
diff --git a/src/HyperDurable.ts b/src/HyperDurable.ts
index a82327d..4da066f 100644
--- a/src/HyperDurable.ts
+++ b/src/HyperDurable.ts
@@ -1,18 +1,18 @@
 import { Router } from 'itty-router';
 import { HyperError } from './HyperError';
 
-interface HyperState extends DurableObjectState {
-  dirty: Set<string>;
+interface HyperState<T> extends DurableObjectState {
+  dirty: Set<Extract<keyof T, string>>;
   initialized?: Promise<void>;
-  persisted: Set<string>;
+  persisted: Set<Extract<keyof T, string>>;
   tempKey: string;
 }
 
-export class HyperDurable<Env = unknown> implements DurableObject {
+export class HyperDurable<T extends object, Env = unknown> implements DurableObject {
   readonly isProxy?: boolean;
   readonly original?: any;
   env: Env;
-  state: HyperState;
+  state: HyperState<T>;
   storage: DurableObjectStorage;
   router: Router;
 
@@ -51,7 +51,9 @@ export class HyperDurable<Env = unknown> implements DurableObject {
 
         // If we're getting a proxied top-level property of the Durable Object,
         // save the key to persist the deeply-nested property
-        if (target[key].isProxy && this === target) this.state.tempKey = key;
+        if (target[key].isProxy && this === target && !reservedKeys.has(key)) {
+          this.state.tempKey = key;
+        }
 
         // If prop is a function, bind `this`
         return typeof target[key] === 'function'
@@ -62,9 +64,9 @@ export class HyperDurable<Env = unknown> implements DurableObject {
         // Add key to persist data
         if (target[key] !== value) {
           if (this === target) {
-            this.state.dirty.add(key);
+            this.state.dirty.add(key as Extract<keyof T, string>);
           } else {
-            this.state.dirty.add(this.state.tempKey);
+            this.state.dirty.add(this.state.tempKey as Extract<keyof T, string>);
           }
         }
 
@@ -202,13 +204,13 @@ export class HyperDurable<Env = unknown> implements DurableObject {
 
   async load() {
     if (this.state.persisted.size === 0) {
-      const persisted = await this.storage.get<Set<string>>('persisted');
+      const persisted = await this.storage.get<Set<Extract<keyof T, string>>>('persisted');
       if (persisted) {
         this.state.persisted = persisted;
       }
     }
     for (let key of this.state.persisted) {
-      this[key] = await this.storage.get(key);
+      this[key as string] = await this.storage.get(key);
     }
   }
 
@@ -217,7 +219,9 @@ export class HyperDurable<Env = unknown> implements DurableObject {
     try {
       let newProps = false;
       for (let key of this.state.dirty) {
-        const value = this[key].isProxy ? this[key].original : this[key];
+        const value = this[key as string].isProxy ?
+          this[key as string].original :
+          this[key as string];
         await this.storage.put(key, value);
         if (!this.state.persisted.has(key)) {
           this.state.persisted.add(key);
@@ -238,7 +242,7 @@ export class HyperDurable<Env = unknown> implements DurableObject {
       await this.storage.deleteAll();
       this.state.dirty.clear();
       for (let key of this.state.persisted) {
-        delete this[key];
+        delete this[key as string];
         this.state.persisted.delete(key);
       }
     } catch(e) {
@@ -248,14 +252,15 @@ export class HyperDurable<Env = unknown> implements DurableObject {
     }
   }
 
-  toObject(): object {
+  toObject(): T {
     const output = {};
     for (let key of this.state.persisted) {
-      output[key] = this[key];
+      output[key as string] = this[key as string];
     }
     for (let key of this.state.dirty) {
-      output[key] = this[key];
+      output[key as string] = this[key as string];
     }
+    // @ts-ignore
     return output;
   }
 
diff --git a/src/HyperNamespaceProxy.ts b/src/HyperNamespaceProxy.ts
index f74806c..b9a9d5e 100644
--- a/src/HyperNamespaceProxy.ts
+++ b/src/HyperNamespaceProxy.ts
@@ -1,9 +1,9 @@
 import { HyperDurable } from './HyperDurable';
 import { HyperError } from './HyperError';
 
-export class HyperNamespaceProxy<T extends HyperDurable<ENV>, ENV> implements DurableObjectNamespace {
+export class HyperNamespaceProxy<DO extends HyperDurable<any, ENV>, ENV> implements DurableObjectNamespace {
   namespace: DurableObjectNamespace;
-  ref: T;
+  ref: DO;
 
   newUniqueId: (_options?: DurableObjectNamespaceNewUniqueIdOptions) => DurableObjectId;
   idFromName: (name: string) => DurableObjectId;
@@ -11,7 +11,7 @@ export class HyperNamespaceProxy<T extends HyperDurable<ENV>, ENV> implements Du
 
   constructor(
     namespace: DurableObjectNamespace,
-    ref: new (state: DurableObjectState, env: ENV) => T
+    ref: new (state: DurableObjectState, env: ENV) => DO
   ) {
     this.namespace = namespace;
     // Create a reference of the DO to check for methods / properties
@@ -41,15 +41,15 @@ export class HyperNamespaceProxy<T extends HyperDurable<ENV>, ENV> implements Du
     // All of our prop getters & methods return Promises, since everything uses the
     // fetch interface.
     type PromisedGetStub = {
-      [Prop in keyof T]?:
-        T[Prop] extends Function
+      [Prop in keyof DO]?:
+        DO[Prop] extends Function
         ? () => Promise<unknown>
         : Promise<unknown>;
     };
     // All of our props have setters formatted as: setProperty()
     type SetStub = {
-      [Prop in keyof T as T[Prop] extends Function ? never : `set${Capitalize<string & Prop>}`]?:
-        (newValue: T[Prop]) => Promise<unknown>
+      [Prop in keyof DO as DO[Prop] extends Function ? never : `set${Capitalize<string & Prop>}`]?:
+        (newValue: DO[Prop]) => Promise<unknown>
     }
     type HyperStub = DurableObjectStub & PromisedGetStub & SetStub;
 
@@ -115,12 +115,12 @@ export class HyperNamespaceProxy<T extends HyperDurable<ENV>, ENV> implements Du
   }
 }
 
-export const proxyHyperDurables = <DO extends HyperDurable<ENV>, ENV>(
-  env: ENV,
-  doBindings: { [key: string]: new (state: DurableObjectState, env: ENV) => DO }
+export const proxyHyperDurables = <DO extends HyperDurable<any, Env>, Env>(
+  env: Env,
+  doBindings: { [key: string]: new (state: DurableObjectState, env: Env) => DO }
 ) => {
   const newEnv: {
-    [Prop in keyof typeof doBindings]?: HyperNamespaceProxy<DO, ENV>
+    [Prop in keyof typeof doBindings]?: HyperNamespaceProxy<DO, Env>
   } = {};
   for (const [key, value] of Object.entries(doBindings)) {
     if (!(value.prototype instanceof HyperDurable)) {
diff --git a/src/index.d.ts b/src/index.d.ts
index 4fe7f5b..3d296a5 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -2,18 +2,18 @@
 
 import { Router } from "itty-router";
 
-export interface HyperState extends DurableObjectState {
-  dirty: Set<string>;
+export interface HyperState<T> extends DurableObjectState {
+  dirty: Set<Extract<keyof T, string>>;
   initialized?: Promise<void>;
-  persisted: Set<string>;
+  persisted: Set<Extract<keyof T, string>>;
   tempKey: string;
 }
 
-export class HyperDurable<Env = unknown> {
+export class HyperDurable<T extends object, Env = unknown> {
   readonly isProxy?: boolean;
   readonly original?: any;
   env: Env;
-  state: HyperState;
+  state: HyperState<T>;
   storage: DurableObjectStorage;
   router: Router;
 
@@ -23,35 +23,35 @@ export class HyperDurable<Env = unknown> {
   load(): Promise<void>;
   persist(): Promise<void>;
   destroy(): Promise<void>
-  toObject(): object;
+  toObject(): T;
   fetch(request: Request): Promise<Response>;
 }
 
-export class HyperNamespaceProxy<T extends HyperDurable<ENV>, ENV> {
+export class HyperNamespaceProxy<DO extends HyperDurable<any, Env>, Env> {
   namespace: DurableObjectNamespace;
-  ref: T;
+  ref: DO;
   newUniqueId: (_options?: DurableObjectNamespaceNewUniqueIdOptions) => DurableObjectId;
   idFromName: (name: string) => DurableObjectId;
   idFromString: (hexId: string) => DurableObjectId;
 
   constructor(
     namespace: DurableObjectNamespace,
-    ref: new (state: DurableObjectState, env: ENV) => T
+    ref: new (state: DurableObjectState, env: Env) => DO
   );
   get(id: DurableObjectId): DurableObjectStub & {
-      [Prop in keyof T]:
-        T[Prop] extends Function
+      [Prop in keyof DO]:
+        DO[Prop] extends Function
         ? () => Promise<unknown>
         : Promise<unknown>;
     } & {
-      [Prop in keyof T as T[Prop] extends Function ? never : `set${Capitalize<string & Prop>}`]:
-        (newValue: T[Prop]) => Promise<unknown>
+      [Prop in keyof DO as DO[Prop] extends Function ? never : `set${Capitalize<string & Prop>}`]:
+        (newValue: DO[Prop]) => Promise<unknown>
     };
 }
 
-export function proxyHyperDurables<DO extends HyperDurable<ENV>, ENV>(
-  env: ENV,
-  doBindings: { [key: string]: new (state: DurableObjectState, env: ENV) => DO }
+export function proxyHyperDurables<DO extends HyperDurable<any, Env>, Env>(
+  env: Env,
+  doBindings: { [key: string]: new (state: DurableObjectState, env: Env) => DO }
 ): {
-  [Prop in keyof typeof doBindings]: HyperNamespaceProxy<DO, ENV>
+  [Prop in keyof typeof doBindings]: HyperNamespaceProxy<DO, Env>
 }
diff --git a/test/counter.ts b/test/counter.ts
index bb651f8..40a2b34 100644
--- a/test/counter.ts
+++ b/test/counter.ts
@@ -1,12 +1,19 @@
 import { HyperDurable } from '../src/HyperDurable';
 
-export class Counter extends HyperDurable<Environment> {
+type CounterData = {
+  abc?: number;
+  counter: number;
+  objectLikeProp: string[];
+}
+
+export class Counter extends HyperDurable<CounterData, Environment> implements CounterData {
   abc?: number;
   counter: number;
   objectLikeProp: string[];
 
   constructor(state: DurableObjectState, env: Environment) {
     super(state, env);
+    
     this.counter = 1;
     this.objectLikeProp = [];
   }