diff --git a/.github/workflows/test_mac.yml b/.github/workflows/test_mac.yml
index de4aebc5..64c3dfa8 100644
--- a/.github/workflows/test_mac.yml
+++ b/.github/workflows/test_mac.yml
@@ -12,7 +12,7 @@ on:
 
 jobs:
   testMac:
-    runs-on: macos-latest
+    runs-on: macos-13
     steps:
       - name: Python Setup
         uses: actions/setup-python@v5
diff --git a/novelwriter/gui/doceditor.py b/novelwriter/gui/doceditor.py
index 08a963e7..29e83a0b 100644
--- a/novelwriter/gui/doceditor.py
+++ b/novelwriter/gui/doceditor.py
@@ -39,8 +39,8 @@ from time import time
 from typing import TYPE_CHECKING
 
 from PyQt5.QtCore import (
-    pyqtSignal, pyqtSlot, QObject, QPoint, QRegExp, QRegularExpression,
-    QRunnable, Qt, QTimer
+    QObject, QPoint, QRegExp, QRegularExpression, QRunnable, Qt, QTimer,
+    pyqtSignal, pyqtSlot
 )
 from PyQt5.QtGui import (
     QColor, QCursor, QFont, QKeyEvent, QKeySequence, QMouseEvent, QPalette,
@@ -65,7 +65,7 @@ from novelwriter.text.counting import standardCounter
 from novelwriter.tools.lipsum import GuiLipsum
 from novelwriter.types import (
     QtAlignCenterTop, QtAlignJustify, QtAlignLeft, QtAlignLeftTop,
-    QtAlignRight, QtKeepAnchor, QtModCtrl, QtMouseLeft, QtModeNone, QtModShift,
+    QtAlignRight, QtKeepAnchor, QtModCtrl, QtModeNone, QtModShift, QtMouseLeft,
     QtMoveAnchor, QtMoveLeft, QtMoveRight
 )
 
@@ -334,7 +334,7 @@ class GuiDocEditor(QPlainTextEdit):
         font = QFont()
         font.setFamily(CONFIG.textFont)
         font.setPointSize(CONFIG.textSize)
-        self.setFont(font)
+        self._qDocument.setDefaultFont(font)
 
         # Set default text margins
         # Due to cursor visibility, a part of the margin must be
diff --git a/novelwriter/gui/docviewer.py b/novelwriter/gui/docviewer.py
index bc5caeb5..f5fbec42 100644
--- a/novelwriter/gui/docviewer.py
+++ b/novelwriter/gui/docviewer.py
@@ -30,7 +30,7 @@ import logging
 
 from enum import Enum
 
-from PyQt5.QtCore import pyqtSignal, pyqtSlot, QPoint, Qt, QUrl
+from PyQt5.QtCore import QPoint, Qt, QUrl, pyqtSignal, pyqtSlot
 from PyQt5.QtGui import (
     QCursor, QFont, QMouseEvent, QPalette, QResizeEvent, QTextCursor,
     QTextOption
@@ -44,7 +44,7 @@ from novelwriter import CONFIG, SHARED
 from novelwriter.common import cssCol
 from novelwriter.constants import nwHeaders, nwUnicode
 from novelwriter.core.tohtml import ToHtml
-from novelwriter.enum import nwItemType, nwDocAction, nwDocMode
+from novelwriter.enum import nwDocAction, nwDocMode, nwItemType
 from novelwriter.error import logException
 from novelwriter.extensions.eventfilters import WheelEventFilter
 from novelwriter.extensions.modified import NIconToolButton
@@ -146,7 +146,7 @@ class GuiDocViewer(QTextBrowser):
         font = QFont()
         font.setFamily(CONFIG.textFont)
         font.setPointSize(CONFIG.textSize)
-        self.setFont(font)
+        self.document().setDefaultFont(font)
 
         # Set the widget colours to match syntax theme
         mainPalette = self.palette()
diff --git a/novelwriter/tools/manussettings.py b/novelwriter/tools/manussettings.py
index 18786ffa..a27c011f 100644
--- a/novelwriter/tools/manussettings.py
+++ b/novelwriter/tools/manussettings.py
@@ -27,13 +27,13 @@ import logging
 
 from typing import TYPE_CHECKING
 
-from PyQt5.QtGui import QFont, QIcon, QSyntaxHighlighter, QTextCharFormat, QTextDocument
 from PyQt5.QtCore import QEvent, Qt, pyqtSignal, pyqtSlot
+from PyQt5.QtGui import QFont, QIcon, QSyntaxHighlighter, QTextCharFormat, QTextDocument
 from PyQt5.QtWidgets import (
-    QAbstractButton, QAbstractItemView, QDialog, QDialogButtonBox,
-    QFontDialog, QFrame, QGridLayout, QHBoxLayout, QHeaderView, QLabel,
-    QLineEdit, QMenu, QPlainTextEdit, QPushButton, QSplitter, QStackedWidget,
-    QTreeWidget, QTreeWidgetItem, QVBoxLayout, QWidget
+    QAbstractButton, QAbstractItemView, QDialog, QDialogButtonBox, QFontDialog,
+    QFrame, QGridLayout, QHBoxLayout, QHeaderView, QLabel, QLineEdit, QMenu,
+    QPlainTextEdit, QPushButton, QSplitter, QStackedWidget, QTreeWidget,
+    QTreeWidgetItem, QVBoxLayout, QWidget
 )
 
 from novelwriter import CONFIG, SHARED
@@ -1060,8 +1060,6 @@ class _FormatTab(NScrollableForm):
     def __init__(self, buildMain: GuiBuildSettings, build: BuildSettings) -> None:
         super().__init__(parent=buildMain)
 
-        self.buildMain = buildMain
-
         self._build = build
         self._unitScale = 1.0
 
diff --git a/pyproject.toml b/pyproject.toml
index b6d40d9d..f8c894ca 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -46,3 +46,22 @@ include = ["novelwriter*"]
 
 [project.gui-scripts]
 novelwriter = "novelwriter:main"
+
+[tool.isort]
+py_version="310"
+line_length = 99
+wrap_length = 79
+multi_line_output = 5
+force_grid_wrap = 0
+lines_between_types = 1
+forced_separate = ["tests.*"]
+
+[tool.flake8]
+max-line-length = 99
+ignore = ["E133", "E221", "E226", "E228", "E241", "W503", "ANN101", "ANN102", "ANN401"]
+per-file-ignores = ["tests/*:ANN"]
+exclude = ["docs/*"]
+
+[tool.autopep8]
+max_line_length = 99
+ignore = ["E133", "E221", "E226", "E228", "E241", "W503"]