diff --git a/build.gradle b/build.gradle
index c16be97..8cb57ac 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.1.60'
+    ext.kotlin_version = '1.2.0'
 
     repositories {
         mavenCentral()
@@ -17,10 +17,12 @@ allprojects {
 
     repositories {
         mavenCentral()
+        maven { url 'https://jitpack.io' }
     }
 
     dependencies {
         compile "org.jetbrains.kotlin:kotlin-stdlib-js:$kotlin_version"
+        compile 'com.github.cypressious.kotlin-webextensions-declarations:webextensions-declarations:v0.1'
     }
 
     compileKotlin2Js {
diff --git a/content_script/src/main/kotlin/content_script.kt b/content_script/src/main/kotlin/content_script.kt
index 141046e..7f59ec4 100644
--- a/content_script/src/main/kotlin/content_script.kt
+++ b/content_script/src/main/kotlin/content_script.kt
@@ -1,5 +1,6 @@
 import org.w3c.dom.HTMLElement
 import org.w3c.dom.asList
+import webextensions.browser
 import kotlin.browser.document
 import kotlin.browser.window
 
@@ -9,7 +10,7 @@ fun main(args: Array<String>) {
     }
     window.asDynamic().hasRun = true
 
-    browser.runtime.onMessage.addListener { message ->
+    browser.runtime.onMessage.addListener { message,_,_ ->
         if (message.command === "beastify") {
             insertBeast(message.beastURL as String)
         } else if (message.command === "reset") {
diff --git a/content_script/src/main/kotlin/helpers.kt b/content_script/src/main/kotlin/helpers.kt
deleted file mode 100644
index 4113c3d..0000000
--- a/content_script/src/main/kotlin/helpers.kt
+++ /dev/null
@@ -1 +0,0 @@
-external val browser: dynamic
\ No newline at end of file
diff --git a/popup/choose_beast.html b/popup/choose_beast.html
index d2a78d1..b5a4c04 100644
--- a/popup/choose_beast.html
+++ b/popup/choose_beast.html
@@ -18,6 +18,7 @@
         <p>Try a different page.</p>
     </div>
     <script src="build/classes/kotlin/main/min/kotlin.js"></script>
+    <script src="build/classes/kotlin/main/min/declarations.js"></script>
     <script src="build/classes/kotlin/main/min/popup.js"></script>
 </body>
 
diff --git a/popup/src/main/kotlin/helpers.kt b/popup/src/main/kotlin/helpers.kt
deleted file mode 100644
index 691fef6..0000000
--- a/popup/src/main/kotlin/helpers.kt
+++ /dev/null
@@ -1,26 +0,0 @@
-import kotlin.js.Promise
-
-external val browser: Browser
-
-external class Browser {
-    val tabs: Tabs
-    val extension: Extension
-}
-
-external class Tabs {
-    fun executeScript(def: Script): Promise<List<Any>>
-    fun insertCSS(id: Int, details: CssDetails): Promise<Unit>
-    fun removeCSS(id: Int, details: CssDetails): Promise<Unit>
-    fun sendMessage(id: Int, message: dynamic): Any
-    fun query(info: Query): Promise<Array<Tab>>
-}
-
-external class Extension {
-    fun getURL(s: String): String
-}
-
-class Tab(val id: Int)
-
-class Script(val file: String)
-class CssDetails(val code: String)
-class Query(val active: Boolean, val currentWindow: Boolean)
\ No newline at end of file
diff --git a/popup/src/main/kotlin/popup.kt b/popup/src/main/kotlin/popup.kt
index c1100d5..ff1a921 100644
--- a/popup/src/main/kotlin/popup.kt
+++ b/popup/src/main/kotlin/popup.kt
@@ -1,16 +1,20 @@
+import extensionTypes.InjectDetails
 import org.w3c.dom.Element
+import tabs.QueryInfo
+import webextensions.browser
 import kotlin.browser.document
 import kotlin.js.Promise
 
-
 const val SCRIPT_PATH = "/content_script/build/classes/kotlin/main/min"
 
 fun main(args: Array<String>) {
     Promise.all(arrayOf(
             browser.tabs.executeScript(
-                    Script("$SCRIPT_PATH/kotlin.js")),
+                    details = InjectDetails(file = "$SCRIPT_PATH/kotlin.js")),
+            browser.tabs.executeScript(
+                    details = InjectDetails(file = "$SCRIPT_PATH/declarations.js")),
             browser.tabs.executeScript(
-                    Script("$SCRIPT_PATH/content_script.js"))
+                    details = InjectDetails(file = "$SCRIPT_PATH/content_script.js"))
     ))
             .then({ listenForClicks() })
             .catch(::reportExecuteScriptError)
@@ -25,8 +29,8 @@ fun listenForClicks() {
     document.addEventListener("click", { e ->
         val target = e.target as? Element ?: return@addEventListener
 
-        browser.tabs.query(Query(active = true, currentWindow = true))
-                .then({ tabs -> handleClick(target, tabs[0].id) })
+        browser.tabs.query(QueryInfo(active = true, currentWindow = true))
+                .then({ tabs -> handleClick(target, tabs[0].id!!) })
                 .catch(::reportError)
     })
 }
@@ -41,13 +45,13 @@ fun handleClick(target: Element, id: Int) {
     if (target.classList.contains("beast")) {
         val url = getUrl(target.textContent)
 
-        browser.tabs.insertCSS(id, CssDetails(CSS_HIDE_PAGE))
+        browser.tabs.insertCSS(id, InjectDetails(code = CSS_HIDE_PAGE))
         browser.tabs.sendMessage(id, jsObject {
             command = "beastify"
             beastURL = url
         })
     } else {
-        browser.tabs.removeCSS(id, CssDetails(CSS_HIDE_PAGE))
+        browser.tabs.removeCSS(id, InjectDetails(code = CSS_HIDE_PAGE))
         browser.tabs.sendMessage(id, jsObject {
             command = "reset"
         })