diff -u b/prepopulate.module b/prepopulate.module
--- b/prepopulate.module
+++ b/prepopulate.module
@@ -16,7 +16,7 @@
   if ($form_state->isRebuilding()) {
     return;
   }
-  if (\Drupal::request()->query->get('edit')) {
+  if (\Drupal::request()->query->has('edit')) {
     $form['#after_build'][] = 'prepopulate_after_build';
   }
 }
diff -u b/src/Populate.php b/src/Populate.php
--- b/src/Populate.php
+++ b/src/Populate.php
@@ -81,17 +81,18 @@
     if (is_array($request_slice)) {
       foreach (array_keys($request_slice) as $request_variable) {
         if (isset($form[$request_variable])) {
-          if (isset($form[$request_variable]['widget'][0]['value']['#type'])) {
-            $type = $form[$request_variable]['widget'][0]['value']['#type'];
+          $element = &$form[$request_variable];
+          if (isset($element['widget'][0]['value']['#type'])) {
+            $type = $element['widget'][0]['value']['#type'];
           }
-          elseif (isset($form[$request_variable]['widget'][0]['target_id']['#type'])) {
-            $type = $form[$request_variable]['widget'][0]['target_id']['#type'];
+          elseif (isset($element['widget'][0]['target_id']['#type'])) {
+            $type = $element['widget'][0]['target_id']['#type'];
           }
-          elseif (isset($form[$request_variable]['widget']['#type'])) {
-            $type = $form[$request_variable]['widget']['#type'];
+          elseif (isset($element['widget']['#type'])) {
+            $type = $element['widget']['#type'];
           }
-          if (Element::child($request_variable) && !empty($form[$request_variable]) && (empty($type) || in_array($type, $this->whitelistedTypes))) {
-            $this->populateForm($form[$request_variable], $request_slice[$request_variable]);
+          if (Element::child($request_variable) && !empty($element) && (empty($type) || in_array($type, $this->whitelistedTypes))) {
+            $this->populateForm($element, $request_slice[$request_variable]);
           }
         }
       }
@@ -127,13 +128,13 @@
    *
    * @param $value
    *   The value.
-   * @param $element
+   * @param array $element
    *   The form element to populate.
    *
    * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
    * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
    */
-  protected function formatEntityAutocomplete($value, &$element) {
+  protected function formatEntityAutocomplete($value, array &$element) {
     $entity = $this->entityTypeManager
       ->getStorage($element['#target_type'])
       ->load($value);