diff --git a/conversejs/.eslintrc.json b/conversejs/.eslintrc.json
index 4ad2d1a6..bd9288c4 100644
--- a/conversejs/.eslintrc.json
+++ b/conversejs/.eslintrc.json
@@ -1,23 +1,40 @@
 {
-    "root": true,
-    "env": {
-        "browser": true,
-        "es6": true
-    },
-    "extends": [
-        "standard"
+  "root": true,
+  "env": {
+      "browser": true,
+      "es6": true
+  },
+  "extends": [
+    "standard-with-typescript"
+  ],
+  "globals": {},
+  "parser": "@typescript-eslint/parser",
+  "parserOptions": {
+      "ecmaVersion": 2018,
+      "project": [
+          "./conversejs/tsconfig.json"
+      ]
+  },
+  "plugins": [
+      "@typescript-eslint"
+  ],
+  "ignorePatterns": [],
+  "rules": {
+    "@typescript-eslint/no-unused-vars": [2, {"argsIgnorePattern": "^_"}],
+    "@typescript-eslint/no-floating-promises": "error",
+    "@typescript-eslint/no-misused-promises": "error",
+    "@typescript-eslint/no-var-requires": "off",
+    "@typescript-eslint/strict-boolean-expressions": "off",
+    "@typescript-eslint/return-await": [2, "in-try-catch"], // FIXME: correct?
+    "@typescript-eslint/no-invalid-void-type": "off",
+    "@typescript-eslint/triple-slash-reference": "off",
+    "max-len": [
+      "error",
+      {
+        "code": 120,
+        "comments": 120
+      }
     ],
-    "globals": {},
-    "plugins": [],
-    "ignorePatterns": [],
-    "rules": {
-        "max-len": [
-          "error",
-          {
-            "code": 120,
-            "comments": 120
-          }
-        ],
-        "no-unused-vars": [2, {"argsIgnorePattern": "^_"}]
-    }
+    "no-unused-vars": "off"
+}
 }
diff --git a/conversejs/builtin.js b/conversejs/builtin.ts
similarity index 86%
rename from conversejs/builtin.js
rename to conversejs/builtin.ts
index ee92bf40..bb72de3c 100644
--- a/conversejs/builtin.js
+++ b/conversejs/builtin.ts
@@ -1,4 +1,12 @@
-function inIframe () {
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+interface Window {
+  converse: {
+    initialize: (args: any) => void
+  }
+  initConverse: (args: any) => void
+}
+
+function inIframe (): boolean {
   try {
     return window.self !== window.top
   } catch (e) {
diff --git a/conversejs/tsconfig.json b/conversejs/tsconfig.json
new file mode 100644
index 00000000..21014bdc
--- /dev/null
+++ b/conversejs/tsconfig.json
@@ -0,0 +1,25 @@
+{
+	"compilerOptions": {
+    "module": "es6",
+    "target": "es5",
+    "allowJs": true,
+		"sourceMap": true,
+		"forceConsistentCasingInFileNames": true,
+		"strict": true,
+		"alwaysStrict": true, // should already be true because of strict:true
+		"noImplicitAny": true, // should already be true because of strict:true
+		"noImplicitThis": true, // should already be true because of strict:true
+		"noImplicitReturns": true,
+		"strictBindCallApply": true, // should already be true because of strict:true
+		"noUnusedLocals": true,
+    "outDir": "../dist/client",
+		"paths": {
+			"shared/*": ["../shared/*"]
+		}
+	},
+	"include": [
+		"./**/*",
+		"../shared/**/*"
+	],
+	"exclude": []
+}
diff --git a/webpack.config.js b/webpack.config.js
index a07c45e7..1362d4a9 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -42,8 +42,16 @@ let config = clientFiles.map(f => ({
 }))
 
 config.push({
-  entry: "./conversejs/builtin.js",
+  entry: "./conversejs/builtin.ts",
   devtool: process.env.NODE_ENV === 'dev' ? 'eval-source-map' : false,
+  module: {
+    rules: [
+      {
+        test: /\.tsx?$/,
+        use: 'ts-loader'
+      }
+    ]
+  },
   output: {
     path: path.resolve(__dirname, "./dist/client/static"),
     filename: "./builtin.js"