diff --git a/.eslintrc.js b/.eslintrc.js
index c0b99a6..66c3718 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -15,6 +15,10 @@ module.exports = {
   },
   plugins: ['sort-keys-fix', 'import'],
   rules: {
+    '@typescript-eslint/no-unused-vars': [
+      'error',
+      { varsIgnorePattern: '^_.*' },
+    ],
     'import/newline-after-import': 'error',
     'import/order': [
       'error',
diff --git a/karma.conf.js b/karma.conf.js
index 1b14228..c82300a 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -1,3 +1,4 @@
+/* eslint-disable @typescript-eslint/no-var-requires */
 
 // Karma configuration
 // Generated on Wed May 27 2020 14:52:46 GMT-0400 (Eastern Daylight Time)
@@ -24,30 +25,28 @@ module.exports = (config) => {
     // list of files / patterns to exclude
     exclude: [],
 
-    karmaTypescriptConfig: {
-      bundlerOptions: {
-        acornOptions: {
-          ecmaVersion: 11,
-        },
-        transforms: [
-          require('karma-typescript-es6-transform')()
-        ]
-      }
-    },
-
     // list of files / patterns to load in the browser
     files: [
       'node_modules/@babel/polyfill/dist/polyfill.js',
       'src/*.ts',
       'src/**/*.ts',
       'test/*.ts',
-      'test/**/*.ts'
+      'test/**/*.ts',
     ],
 
     // frameworks to use
     // available frameworks: https://npmjs.org/browse/keyword/karma-adapter
     frameworks: ['jasmine', 'karma-typescript'],
 
+    karmaTypescriptConfig: {
+      bundlerOptions: {
+        acornOptions: {
+          ecmaVersion: 11,
+        },
+        transforms: [require('karma-typescript-es6-transform')()],
+      },
+    },
+
     // level of logging
     // possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
     logLevel: config.LOG_INFO,
diff --git a/src/connector.ts b/src/connector.ts
index 5c09de7..e350da7 100644
--- a/src/connector.ts
+++ b/src/connector.ts
@@ -12,8 +12,8 @@ import { hasValue } from './util';
 
 type SystemProtocol = {
   ping: {
-    body: {};
-    response: {};
+    body: Record<string, unknown>;
+    response: Record<string, unknown>;
   };
 };
 
@@ -146,7 +146,7 @@ function handleTell0<
 function handleAsk0<
   P extends Protoframe,
   T extends ProtoframeMessageType<P>,
-  R extends ProtoframeMessageResponse<P, T> & {}
+  R extends ProtoframeMessageResponse<P, T> & Record<string, unknown>
 >(
   thisWindow: Window,
   targetWindow: Window,
@@ -190,7 +190,7 @@ async function ask0<
   P extends Protoframe,
   T extends ProtoframeMessageType<P>,
   B extends ProtoframeMessageBody<P, T>,
-  R extends ProtoframeMessageResponse<P, T> & {}
+  R extends ProtoframeMessageResponse<P, T> & Record<string, unknown>
 >(
   thisWindow: Window,
   targetWindow: Window,
@@ -275,7 +275,7 @@ interface AbstractProtoframePubsub<P extends Protoframe>
   ask<
     T extends ProtoframeMessageType<P>,
     B extends ProtoframeMessageBody<P, T>,
-    R extends ProtoframeMessageResponse<P, T> & {}
+    R extends ProtoframeMessageResponse<P, T> & Record<string, unknown>
   >(
     type: T,
     body: B,
@@ -291,7 +291,7 @@ interface AbstractProtoframePubsub<P extends Protoframe>
    */
   handleAsk<
     T extends ProtoframeMessageType<P>,
-    R extends ProtoframeMessageResponse<P, T> & {}
+    R extends ProtoframeMessageResponse<P, T> & Record<string, unknown>
   >(
     type: T,
     handler: (body: ProtoframeMessageBody<P, T>) => Promise<R>,
@@ -532,7 +532,7 @@ export class ProtoframePubsub<P extends Protoframe>
 
   public handleAsk<
     T extends ProtoframeMessageType<P>,
-    R extends P[T]['response'] & {}
+    R extends P[T]['response'] & Record<string, unknown>
   >(type: T, handler: (body: P[T]['body']) => Promise<R>): void {
     this.listeners.push(
       handleAsk0(
@@ -549,7 +549,7 @@ export class ProtoframePubsub<P extends Protoframe>
   public ask<
     T extends ProtoframeMessageType<P>,
     B extends P[T]['body'],
-    R extends P[T]['response'] & {}
+    R extends P[T]['response'] & Record<string, unknown>
   >(type: T, body: B, timeout = 10000): Promise<R> {
     return ask0(
       this.thisWindow,
diff --git a/src/types.ts b/src/types.ts
index 5c5d089..e28fbad 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,7 +1,7 @@
 /** The protocol type that holds your message types and their schema. */
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 export type Protoframe = Record<string, ProtoframeEntry<any, any>>;
-export type ProtoframeEntry<B, R extends {}> = {
+export type ProtoframeEntry<B, R extends Record<string, unknown>> = {
   body: B;
   response?: R;
 };