diff --git a/src/theme-package.coffee b/src/theme-package.coffee
deleted file mode 100644
index 053132d61..000000000
--- a/src/theme-package.coffee
+++ /dev/null
@@ -1,37 +0,0 @@
-path = require 'path'
-Package = require './package'
-
-module.exports =
-class ThemePackage extends Package
-  getType: -> 'theme'
-
-  getStyleSheetPriority: -> 1
-
-  enable: ->
-    @config.unshiftAtKeyPath('core.themes', @name)
-
-  disable: ->
-    @config.removeAtKeyPath('core.themes', @name)
-
-  preload: ->
-    @loadTime = 0
-    @configSchemaRegisteredOnLoad = @registerConfigSchemaFromMetadata()
-
-  finishLoading: ->
-    @path = path.join(@packageManager.resourcePath, @path)
-
-  load: ->
-    @loadTime = 0
-    @configSchemaRegisteredOnLoad = @registerConfigSchemaFromMetadata()
-    this
-
-  activate: ->
-    @activationPromise ?= new Promise (resolve, reject) =>
-      @resolveActivationPromise = resolve
-      @rejectActivationPromise = reject
-      @measure 'activateTime', =>
-        try
-          @loadStylesheets()
-          @activateNow()
-        catch error
-          @handleError("Failed to activate the #{@name} theme", error)
diff --git a/src/theme-package.js b/src/theme-package.js
new file mode 100644
index 000000000..7ac01bd97
--- /dev/null
+++ b/src/theme-package.js
@@ -0,0 +1,55 @@
+const path = require('path')
+const Package = require('./package')
+
+module.exports =
+class ThemePackage extends Package {
+  getType () {
+    return 'theme'
+  }
+
+  getStyleSheetPriority () {
+    return 1
+  }
+
+  enable () {
+    this.config.unshiftAtKeyPath('core.themes', this.name)
+  }
+
+  disable () {
+    this.config.removeAtKeyPath('core.themes', this.name)
+  }
+
+  preload () {
+    this.loadTime = 0
+    this.configSchemaRegisteredOnLoad = this.registerConfigSchemaFromMetadata()
+  }
+
+  finishLoading () {
+    this.path = path.join(this.packageManager.resourcePath, this.path)
+  }
+
+  load () {
+    this.loadTime = 0
+    this.configSchemaRegisteredOnLoad = this.registerConfigSchemaFromMetadata()
+    return this
+  }
+
+  activate () {
+    if (this.activationPromise == null) {
+      this.activationPromise = new Promise((resolve, reject) => {
+        this.resolveActivationPromise = resolve
+        this.rejectActivationPromise = reject
+        this.measure('activateTime', () => {
+          try {
+            this.loadStylesheets()
+            this.activateNow()
+          } catch (error) {
+            this.handleError(`Failed to activate the ${this.name} theme`, error)
+          }
+        })
+      })
+    }
+
+    return this.activationPromise
+  }
+}