diff --git a/src/calibre/gui2/convert/regex_builder.py b/src/calibre/gui2/convert/regex_builder.py
index a4ca4eaf11..8b7ac30296 100644
--- a/src/calibre/gui2/convert/regex_builder.py
+++ b/src/calibre/gui2/convert/regex_builder.py
@@ -4,7 +4,7 @@
 import os
 from contextlib import suppress
 from qt.core import (
-    QApplication, QBrush, QDialog, QDialogButtonBox, Qt, QTextCursor,
+    QBrush, QDialog, QDialogButtonBox, Qt, QTextCursor,
     QTextEdit, pyqtSignal
 )