diff --git a/index.js b/index.js
index 204fc0e2..2b4f9286 100644
--- a/index.js
+++ b/index.js
@@ -27,41 +27,44 @@ module.exports = {
     }
   },
 
-  setupPreprocessorRegistry(type, registry) {
-    if (type === 'parent') {
-      this._assignOptions(this.app);
-
-      let pluginFnName = this._stripTestSelectors ? '_buildStripPlugin' : '_buildHashParamPlugin';
-
-      let plugin = this[pluginFnName]();
-      plugin.parallelBabel = {
-        requireFile: __filename,
-        buildUsing: pluginFnName,
-        params: {},
-      };
+  _setupPreprocessorRegistry(registry) {
+    let pluginFnName = this._stripTestSelectors ? '_buildStripPlugin' : '_buildHashParamPlugin';
+
+    let plugin = this[pluginFnName]();
+    plugin.parallelBabel = {
+      requireFile: __filename,
+      buildUsing: pluginFnName,
+      params: {},
+    };
 
-      registry.add('htmlbars-ast-plugin', plugin);
-    }
+    registry.add('htmlbars-ast-plugin', plugin);
   },
 
-  included(app) {
+  included(appOrParent) {
     this._super.included.apply(this, arguments);
 
+    let host = this._findHost();
+    this._assignOptions(host);
+
+    // we can't use the setupPreprocessorRegistry() hook as it is called too
+    // early and we do not have reliable access to `app.tests` there yet
+    this._setupPreprocessorRegistry(appOrParent.registry);
+
     // add the StripDataTestPropertiesPlugin to the list of plugins used by
     // the `ember-cli-babel` addon
     if (this._stripTestSelectors && !this._registeredWithBabel) {
       let checker = new VersionChecker(this.parent).for('ember-cli-babel', 'npm');
 
-      app.options = app.options || {};
+      appOrParent.options = appOrParent.options || {};
 
       if (checker.satisfies('^5.0.0')) {
-        app.options.babel = app.options.babel || {};
-        app.options.babel.plugins = app.options.babel.plugins || [];
-        app.options.babel.plugins.push(require('./strip-data-test-properties-plugin'));
+        appOrParent.options.babel = appOrParent.options.babel || {};
+        appOrParent.options.babel.plugins = appOrParent.options.babel.plugins || [];
+        appOrParent.options.babel.plugins.push(require('./strip-data-test-properties-plugin'));
       } else if (checker.satisfies('^6.0.0-beta.1') || checker.satisfies('^7.0.0')) {
-        app.options.babel6 = app.options.babel6 || {};
-        app.options.babel6.plugins = app.options.babel6.plugins || [];
-        app.options.babel6.plugins.push(require.resolve('./strip-data-test-properties-plugin6'));
+        appOrParent.options.babel6 = appOrParent.options.babel6 || {};
+        appOrParent.options.babel6.plugins = appOrParent.options.babel6.plugins || [];
+        appOrParent.options.babel6.plugins.push(require.resolve('./strip-data-test-properties-plugin6'));
       } else {
         this.ui.writeWarnLine('ember-test-selectors: You are using an unsupported ember-cli-babel version. data-test ' +
           'properties are not automatically stripped from your JS code.');
@@ -71,7 +74,7 @@ module.exports = {
     }
 
     if (!this._stripTestSelectors) {
-      this.app.import('vendor/ember-test-selectors/patch-component.js');
+      host.import('vendor/ember-test-selectors/patch-component.js');
     }
   },