diff --git a/src/WebformCivicrmPreProcess.php b/src/WebformCivicrmPreProcess.php
index 0e40fcf99..5344f2498 100644
--- a/src/WebformCivicrmPreProcess.php
+++ b/src/WebformCivicrmPreProcess.php
@@ -103,6 +103,14 @@ public function alterForm() {
     $this->form['#attributes']['data-form-defaults'] = Json::encode($this->getWebformDefaults());
     // Early return if the form (or page) was already submitted
     $triggering_element = $this->form_state->getTriggeringElement();
+
+    // When user uploads a file using a managed_file element, avoid making any change to $this->form.
+    if ($this->form_state->hasFileElement()
+      && is_array($triggering_element['#submit'])
+      && in_array('file_managed_file_submit', $triggering_element['#submit'], TRUE)) {
+      return;
+    }
+
     if ($triggering_element && $triggering_element['#id'] == 'edit-wizard-prev'
       || (empty($this->form_state->isRebuilding()) && !empty($this->form_state->getValues()) && empty($this->form['#submission']->is_draft))
       // When resuming from a draft