diff --git a/chinese/edit.py b/chinese/edit.py
index b9c5e39..7b76cb2 100644
--- a/chinese/edit.py
+++ b/chinese/edit.py
@@ -17,8 +17,14 @@
 # You should have received a copy of the GNU General Public License along with
 # Chinese Support Redux.  If not, see <https://www.gnu.org/licenses/>.
 
+import re
+import json
+
+import anki.buildinfo
 from anki.hooks import addHook
+from aqt.utils import showWarning
 from aqt import mw
+from aqt.editor import Editor
 
 from .behavior import update_fields
 from .main import config
@@ -80,12 +86,95 @@ def onFocusLost(self, _, note, index):
         return False
 
 
-def append_tone_styling(editor):
-    js = 'var css = document.styleSheets[0];'
+TONE_CSS_RULE = re.compile("(\\.tone\\d) *\\{([^}]*)\\}")
+
+# append_tone_styling(editor: Editor)
+#
+# Extracts the CSS rules for tones (i.e. matching TONE_CSS_RULE) from the 
+# user defined CSS style sheet. For the sake of simplicity, a tone CSS rule
+# must be a one liner.
+#
+# IMPLEMENTATION NOTES:
+#
+# The code makes heavily use of internal APIs in Anki that may change in
+# future releases. Hopefully, these notes are useful to adapt the code to
+# new releases in case of breaking.
+#
+# The solution is based on Anki 2.1.54.
+#
+# The Javascript code being evaluated in the QWebView executes the following steps:
+#   1. Wait until the UI has been loaded. The code for that is based on [1].
+#   2. Loop through all RichTextInput Svelte component instances. They are
+#      reachable via "require" because they have been registered before here [2].
+#      Unfortunately, this method is only available since 2.1.54.
+#   3. Using the RichTextInputAPI [3], we can query the associated CustomStyles
+#      instance. A CustomStyles instance has a `styleMap` [4] that contains an 
+#      "userBase" entry, which wraps a <style> HTML element. This style element's
+#      intended function is to apply color, font family, font size, etc. [5,6].
+#      It is the perfect place to add our own CSS tone rules.
+#
+# [1] https://github.com/ankitects/anki/blob/2.1.54/qt/aqt/editor.py#L184
+# [2] https://github.com/ankitects/anki/blob/2.1.54/ts/editor/rich-text-input/RichTextInput.svelte#L40
+# [3] https://github.com/ankitects/anki/blob/2.1.54/ts/editor/rich-text-input/RichTextInput.svelte#L21
+# [4] https://github.com/ankitects/anki/blob/2.1.54/ts/editor/rich-text-input/CustomStyles.svelte#L37
+# [5] https://github.com/ankitects/anki/blob/2.1.54/ts/editor/rich-text-input/RichTextStyles.svelte#L17
+# [6] https://github.com/ankitects/anki/blob/2.1.54/ts/editor/rich-text-input/RichTextStyles.svelte#L33
+
+def append_tone_styling_anki2_1_54(editor: Editor):
+    rules = []
+    for line in editor.note.note_type()['css'].split('\n'):
+        if '.tone' in line:
+            m = TONE_CSS_RULE.search(line)
+            if m:
+                rules.append(line)
+            else:
+                showWarning("WARN: could not parse CSS tone rule. "
+                            "Currently, tone CSS rules need to be one liners.")
+
+    js = f"var CSSRULES = {json.dumps(rules)};"
+    js += """
+    require("anki/ui").loaded.then(() => 
+      require("anki/RichTextInput").instances.forEach(inst =>
+        inst.customStyles.then(styles => {
+          var sheet = styles.styleMap.get("userBase").element.sheet;
+          CSSRULES.forEach(rule =>
+            sheet.insertRule(rule)
+          );
+        })
+      )
+    );
+    """
+    editor.web.eval(js)
 
-    for line in editor.note.model()['css'].split('\n'):
+def append_tone_styling_anki2_1_49(editor):
+    rules = []
+    for line in editor.note.note_type()['css'].split('\n'):
         if line.startswith('.tone'):
-            js += 'css.insertRule("{}", css.cssRules.length);'.format(
-                line.rstrip())
+            m = TONE_CSS_RULE.search(line)
+            if m:
+                rules.append((m.group(1), m.group(2)))
+            else:
+                showWarning("WARN: could not parse CSS tone rule. "
+                            "Currently, tone CSS rules need to be one liners.")
+
+    inner_js = ""
+    for rulename, ruledef in rules:
+        for part in ruledef.split(';'):
+            if ':' in part:
+                [property, value] = part.split(':', 1)
+                inner_js += f"jQuery('{rulename.strip()}', this.shadowRoot).css('{property.strip()}', '{value.strip()}');\n"
+    js = "jQuery('div.field').each(function () {\n%s})" % inner_js
 
     editor.web.eval(js)
+
+
+__version = [int(x) for x in anki.buildinfo.version.split('.')]
+if __version < [2,1,50]:
+    append_tone_styling = append_tone_styling_anki2_1_49
+elif __version >= [2,1,54]:
+    append_tone_styling = append_tone_styling_anki2_1_54
+else:
+    showWarning("Chinese tone styling has not been implemented for your current Anki version. "
+                "Supported versions are Anki 2.1.49 as well as 2.1.54 and later.")
+    def append_tone_styling(editor):
+        pass
\ No newline at end of file