diff --git a/CHANGELOG.md b/CHANGELOG.md
index d2ebb02..4cc73e8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 Unreleased
 - New: Rename a card
+- Fix: Use a regex validator instead of input mask for Libby setup code due to wonkiness, ref #14
 
 Version 0.1.9 - 2023-09-19
 - Fix: Error on launch for calibre <6.2.0
diff --git a/calibre-plugin/config.py b/calibre-plugin/config.py
index 062c8dd..3784014 100644
--- a/calibre-plugin/config.py
+++ b/calibre-plugin/config.py
@@ -36,6 +36,8 @@
     QWidget,
     Qt,
     QTimer,
+    QRegularExpressionValidator,
+    QRegularExpression,
 )
 
 from . import DEMO_MODE, PLUGIN_NAME, PLUGINS_FOLDER_NAME, logger
@@ -227,7 +229,10 @@ def __init__(self, plugin_action):
         self.libby_setup_code_txt.setPlaceholderText(
             PreferenceTexts.LIBBY_SETUP_CODE_DESC
         )
-        self.libby_setup_code_txt.setInputMask("99999999")
+        self.libby_setup_code_txt.setValidator(
+            QRegularExpressionValidator(QRegularExpression(r"\d{8}"))
+        )
+
         if not DEMO_MODE:
             self.libby_setup_code_txt.setText(PREFS[PreferenceKeys.LIBBY_SETUP_CODE])
         libby_layout.addRow(self.libby_setup_code_lbl, self.libby_setup_code_txt)