diff --git a/commerce_popular_products.module b/commerce_popular_products.module
index 4df68ce24ab136213ff800481320be5149044d27..f3c42267e198e09ce65b3b58ea4e09c0bb623ece 100644
--- a/commerce_popular_products.module
+++ b/commerce_popular_products.module
@@ -199,12 +199,20 @@ function commerce_popular_products_settings_form($form, &$form_state) {
     '#description' => t('The title of the "popular products" block as shown to users.'),
     '#default_value' => $title,
   );
-  $form['product_types'] = array(
-    '#type' => 'checkboxes',
-    '#title' => t('Product Types.'),
-    '#description' => t('Product nodes to include in the popularity check.'),
-    '#default_value' => $products,
-  );
+  if (isset($products)) {
+    $form['product_types'] = array(
+      '#type' => 'checkboxes',
+      '#title' => t('Product Types.'),
+      '#description' => t('Product nodes to include in the popularity check.'),
+      '#default_value' => $products,
+    );
+  }
+  else {
+    $form['product_types'] = array(
+      '#title' => t('Product Types.'),
+      '#markup' => t('<h4>Product types</h4><p>You have not defined any product types. You need to define some first.</p>'),
+    );
+  }
   $product_types = commerce_popular_products_get_product_types();
   $options = array();
   foreach ($product_types as $type) {
@@ -260,6 +268,7 @@ function commerce_popular_products_settings_form_submit($form, &$form_state) {
  * A simple query to return all the Commerce product types in the database.
  */
 function commerce_popular_products_get_product_types() {
+  $names = array();
   $products = commerce_product_types();
   foreach ($products as $item) {
     $names[] = $item['name'];