--- a/eric6/Preferences/SubstyleDefinitionDialog.py	Mon Mar 01 17:48:43 2021 +0100
+++ b/eric6/Preferences/SubstyleDefinitionDialog.py	Tue Mar 02 17:17:09 2021 +0100
@@ -52,7 +52,7 @@
         """
         Private slot to update the state of the OK button.
         """
-        self.buttonBox.button(QDialogButtonBox.Ok).setEnabled(
+        self.buttonBox.button(QDialogButtonBox.StandardButton.Ok).setEnabled(
             bool(self.descriptionEdit.text().strip()) and
             bool(self.wordsEdit.toPlainText().strip())
         )