diff --git a/resource/RosTfTree.ui b/resource/RosTfTree.ui
index 27f197e..52628b4 100644
--- a/resource/RosTfTree.ui
+++ b/resource/RosTfTree.ui
@@ -171,7 +171,7 @@
    <item>
     <widget class="InteractiveGraphicsView" name="graphics_view">
      <property name="renderHints">
-      <set>QPainter::Antialiasing|QPainter::HighQualityAntialiasing|QPainter::SmoothPixmapTransform|QPainter::TextAntialiasing</set>
+      <set>QPainter::Antialiasing|QPainter::SmoothPixmapTransform|QPainter::TextAntialiasing</set>
      </property>
      <property name="resizeAnchor">
       <enum>QGraphicsView::AnchorViewCenter</enum>
diff --git a/src/rqt_tf_tree/dotcode_tf.py b/src/rqt_tf_tree/dotcode_tf.py
index 878f2e0..6a69b17 100644
--- a/src/rqt_tf_tree/dotcode_tf.py
+++ b/src/rqt_tf_tree/dotcode_tf.py
@@ -96,12 +96,16 @@ def generate_dotcode(self,
 
             yaml_data = tf2_frame_srv.call(FrameGraph.Request()).frame_yaml
 
-            def default_tftree_construct_mapping(self, node, deep=False):
-                data = self.construct_mapping_org(node, deep)
-                return {(str(key) if isinstance(key, int) else key): data[key] for key in data}
-
-            yaml.SafeLoader.construct_mapping_org = yaml.SafeLoader.construct_mapping
-            yaml.SafeLoader.construct_mapping = default_tftree_construct_mapping
+            # Patch SafeLoader.construct_mapping only once. Re-patching would
+            # save the already-patched function as construct_mapping_org,
+            # causing it to call itself recursively (RecursionError).
+            if not hasattr(yaml.SafeLoader, 'construct_mapping_org'):
+                def default_tftree_construct_mapping(self, node, deep=False):
+                    data = self.construct_mapping_org(node, deep)
+                    return {(str(key) if isinstance(key, int) else key): data[key] for key in data}
+
+                yaml.SafeLoader.construct_mapping_org = yaml.SafeLoader.construct_mapping
+                yaml.SafeLoader.construct_mapping = default_tftree_construct_mapping
 
             data = yaml_parser.safe_load(yaml_data)
             self.graph = self.generate(data, timer.now().nanoseconds / S_TO_NS)
diff --git a/src/rqt_tf_tree/tf_tree.py b/src/rqt_tf_tree/tf_tree.py
index a2ee7fe..7809b36 100644
--- a/src/rqt_tf_tree/tf_tree.py
+++ b/src/rqt_tf_tree/tf_tree.py
@@ -85,7 +85,7 @@ def __init__(self, context):
             self._widget.setWindowTitle(self._widget.windowTitle() + (' (%d)' % context.serial_number()))
 
         self._scene = QGraphicsScene()
-        self._scene.setBackgroundBrush(Qt.white)
+        self._scene.setBackgroundBrush(Qt.GlobalColor.white)
         self._widget.graphics_view.setScene(self._scene)
 
         self._widget.clear_buffer_push_button.setIcon(QIcon.fromTheme('edit-delete'))
@@ -96,7 +96,10 @@ def __init__(self, context):
 
         self._widget.highlight_connections_check_box.toggled.connect(self._redraw_graph_view)
         self._widget.auto_fit_graph_check_box.toggled.connect(self._redraw_graph_view)
-        self._widget.fit_in_view_push_button.setIcon(QIcon.fromTheme('zoom-original'))
+        # 'zoom-fit-best' is the freedesktop standard name; fall back to the
+        # legacy 'zoom-best-fit' for themes (e.g. ubuntu-mono-*) that lack it.
+        self._widget.fit_in_view_push_button.setIcon(
+            QIcon.fromTheme('zoom-fit-best', QIcon.fromTheme('zoom-best-fit')))
         self._widget.fit_in_view_push_button.pressed.connect(self._fit_in_view)
 
         self._widget.load_dot_push_button.setIcon(QIcon.fromTheme('document-open'))
@@ -109,7 +112,7 @@ def __init__(self, context):
         self._widget.save_as_image_push_button.pressed.connect(self._save_image)
 
         self._deferred_fit_in_view.connect(self._fit_in_view,
-                                           Qt.QueuedConnection)
+                                           Qt.ConnectionType.QueuedConnection)
         self._deferred_fit_in_view.emit()
 
         context.add_widget(self._widget)
@@ -206,7 +209,7 @@ def _load_dot(self, file_name=None):
 
     def _fit_in_view(self):
         self._widget.graphics_view.fitInView(self._scene.itemsBoundingRect(),
-                                             Qt.KeepAspectRatio)
+                                             Qt.AspectRatioMode.KeepAspectRatio)
 
     def _save_dot(self):
         file_name, _ = QFileDialog.getSaveFileName(self._widget,
@@ -217,10 +220,13 @@ def _save_dot(self):
             return
 
         file = QFile(file_name)
-        if not file.open(QIODevice.WriteOnly | QIODevice.Text):
+        if not file.open(QIODevice.OpenModeFlag.WriteOnly | QIODevice.OpenModeFlag.Text):
             return
 
-        file.write(self._current_dotcode)
+        dotcode = self._current_dotcode
+        if isinstance(dotcode, str):
+            dotcode = dotcode.encode()
+        file.write(dotcode)
         file.close()
 
     def _save_svg(self):
@@ -237,7 +243,7 @@ def _save_svg(self):
         generator.setSize((self._scene.sceneRect().size() * 2.0).toSize())
 
         painter = QPainter(generator)
-        painter.setRenderHint(QPainter.Antialiasing)
+        painter.setRenderHint(QPainter.RenderHint.Antialiasing)
         self._scene.render(painter)
         painter.end()
 
@@ -251,9 +257,9 @@ def _save_image(self):
             return
 
         img = QImage((self._scene.sceneRect().size() * 2.0).toSize(),
-                     QImage.Format_ARGB32_Premultiplied)
+                     QImage.Format.Format_ARGB32_Premultiplied)
         painter = QPainter(img)
-        painter.setRenderHint(QPainter.Antialiasing)
+        painter.setRenderHint(QPainter.RenderHint.Antialiasing)
         self._scene.render(painter)
         painter.end()
         img.save(file_name)