diff --git a/plinth/modules/calibre/templates/calibre-delete-library.html b/plinth/modules/calibre/templates/calibre-delete-library.html
index 93946e251..97bb67d88 100644
--- a/plinth/modules/calibre/templates/calibre-delete-library.html
+++ b/plinth/modules/calibre/templates/calibre-delete-library.html
@@ -20,7 +20,7 @@
     {% endblocktrans %}
   </p>
 
-  <form class="form" method="post">
+  <form class="form form-delete" method="post">
     {% csrf_token %}
 
     <input type="submit" class="btn btn-md btn-danger"
diff --git a/plinth/modules/calibre/tests/test_functional.py b/plinth/modules/calibre/tests/test_functional.py
index fabd485b7..6ddd7049f 100644
--- a/plinth/modules/calibre/tests/test_functional.py
+++ b/plinth/modules/calibre/tests/test_functional.py
@@ -62,7 +62,7 @@ def _add_library(browser, name):
     browser.links.find_by_href(
         '/plinth/apps/calibre/library/create/').first.click()
     browser.find_by_id('id_calibre-name').fill(name)
-    functional.submit(browser)
+    functional.submit(browser, form_class='form-calibre')
 
 
 def _delete_library(browser, name, ignore_missing=False):
@@ -77,7 +77,7 @@ def _delete_library(browser, name, ignore_missing=False):
         raise ValueError('Library not found')
 
     link.first.click()
-    functional.submit(browser)
+    functional.submit(browser, form_class='form-delete')
 
 
 def _is_library_available(browser, name):